问题


There is a single choice question about college mathematics. Answer the question by replying A, B, C or D.
Question: In xyz-space, what are the coordinates of the point on the plane 2x + y + 3z = 3 that is closest to the origin?
A. (0, 0, 1)
B. (3/7, 3/14, 9/14)
C. (7/15, 8/15, 1/15)
D. (5/6, 1/3, 1/3)
Answer:

答案

模型 模型答案 正确答案
金声玉亮2.0 B. (3/7, 3/14, 9/14) B
deepseekr1

The closest point on the plane \(2x + y + 3z = 3\) to the origin lies along the line perpendicular to the plane passing through the origin. The normal vector of the plane is \((2, 1, 3)\), so the parametric equations for the line are \(x = 2t\), \(y = t\), \(z = 3t\). Substituting into the plane equation:

\[
2(2t) + t + 3(3t) = 3 \implies 14t = 3 \implies t = \frac{3}{14}.
\]

This gives the coordinates \(\left(\frac{3}{7}, \frac{3}{14}, \frac{9}{14}\right)\), corresponding to **option B**. Verification using the projection formula confirms this result. Checking other options, while option D satisfies the plane equation, its distance from the origin is greater than that of B. Thus, the correct answer is:

**B. (3/7, 3/14, 9/14)**
B
gpto1 B B
GPT-4o To find the point on the plane \(2x + y + 3z = 3\) that is closest to the origin, we need to minimize the distance between a point \((x, y, z)\) on the plane and the origin \((0, 0, 0)\).

The distance \(d\) from the origin to a point \((x, y, z)\) is given by:
\[ d = \sqrt{x^2 + y^2 + z^2} \]

Since we are minimizing \(d\), we can minimize \(d^2\) instead:
\[ d^2 = x^2 + y^2 + z^2 \]

We need to do this minimization subject to the constraint provided by the plane equation:
\[ 2x + y + 3z = 3 \]

Using the method of Lagrange multipliers, we introduce a Lagrange multiplier \(\lambda\) and define the Lagrangian:
\[ \mathcal{L}(x, y, z, \lambda) = x^2 + y^2 + z^2 + \lambda (2x + y + 3z - 3) \]

We take the partial derivatives of \(\mathcal{L}\) with respect to \(x\), \(y\), \(z\), and \(\lambda\) and set them to zero:
\[ \frac{\partial \mathcal{L}}{\partial x} = 2x + 2\lambda = 0 \]
\[ \frac{\partial \mathcal{L}}{\partial y} = 2y + \lambda = 0 \]
\[ \frac{\partial \mathcal{L}}{\partial z} = 2z + 3\lambda = 0 \]
\[ \frac{\partial \mathcal{L}}{\partial \lambda} = 2x + y + 3z - 3 = 0 \]

From \(\frac{\partial \mathcal{L}}{\partial x} = 0\), we get:
\[ 2x + 2\lambda = 0 \implies x = -\lambda \]

From \(\frac{\partial \mathcal{L}}{\partial y} = 0\), we get:
\[ 2y + \lambda = 0 \implies y = -\frac{\lambda}{2} \]

From \(\frac{\partial \mathcal{L}}{\partial z} = 0\), we get:
\[ 2z + 3\lambda = 0 \implies z = -\frac{3\lambda}{2} \]

Substitute \(x = -\lambda\), \(y = -\frac{\lambda}{2}\), and \(z = -\frac{3\lambda}{2}\) into the plane equation:
\[ 2(-\lambda) + \left(-\frac{\lambda}{2}\right) + 3\left(-\frac{3\lambda}{2}\right) = 3 \]
\[ -2\lambda - \frac{\lambda}{2} - \frac{9\lambda}{2} = 3 \]
\[ -2\lambda - \frac{10\lambda}{2} = 3 \]
\[ -2\lambda - 5\lambda = 3 \]
\[ -7\lambda = 3 \]
\[ \lambda = -\frac{3}{7} \]

Thus, we have:
\[ x = -\lambda = \frac{3}{7} \]
\[ y = -\frac{\lambda}{2} = \frac{3}{14} \]
\[ z = -\frac{3\lambda}{2} = \frac{9}{14} \]

Therefore, the coordinates of the point on the plane that is closest to the origin are:
\[ \left( \frac{3}{7}, \frac{3}{14}, \frac{9}{14} \right) \]

The correct answer is:
\[ \boxed{B} \]
B
llama3.1-70B-Instruct

B
B
llama3.1-405B-Instruct

A.
The best answer is A.
B
DeepSeek-Coder-V2 To find the point on the plane \(2x + y + 3z = 3\) that is closest to the origin, we can use the method of finding the point where the normal vector from the origin intersects the plane.

1. **Normal Vector to the Plane**: The coefficients of \(x\), \(y\), and \(z\) in the plane equation give us the normal vector to the plane. Here, the normal vector is \(\mathbf{n} = (2, 1, 3)\).

2. **Direction Vector from Origin**: The direction vector from the origin to the plane in the direction of the normal vector is also \((2, 1, 3)\).

3. **Parameterization**: Let the point on the plane closest to the origin be \((2t, t, 3t)\) for some parameter \(t\).

4. **Substitute into Plane Equation**: Substitute \((2t, t, 3t)\) into the plane equation \(2x + y + 3z = 3\):
\[
2(2t) + t + 3(3t) = 3
\]
Simplify:
\[
4t + t + 9t = 3
\]
\[
14t = 3
\]
\[
t = \frac{3}{14}
\]

5. **Find the Point**: Substitute \(t = \frac{3}{14}\) back into the parameterization \((2t, t, 3t)\):
\[
(2 \cdot \frac{3}{14}, \frac{3}{14}, 3 \cdot \frac{3}{14}) = \left(\frac{6}{14}, \frac{3}{14}, \frac{9}{14}\right) = \left(\frac{3}{7}, \frac{3}{14}, \frac{9}{14}\right)
\]

Thus, the coordinates of the point on the plane \(2x + y + 3z = 3\) that is closest to the origin are \(\left(\frac{3}{7}, \frac{3}{14}, \frac{9}{14}\right)\).

Answer: B
B
Qwen2-72B-Instruct B. (3/7, 3/14, 9/14) B
baichuan4 To find the point on the plane 2x + y + 3z = 3 that is closest to the origin, we need to minimize the distance from the origin to a point on the plane. The distance from the origin (0, 0, 0) to a point (x, y, z) on the plane is given by the Euclidean distance formula:

distance = √(x^2 + y^2 + z^2)

We want to minimize this distance subject to the constraint that the point (x, y, z) lies on the plane 2x + y + 3z = 3. To do this, we can use the method of Lagrange multipliers.

The Lagrangian function is given by:

L(x, y, z, λ) = x^2 + y^2 + z^2 + λ(2x + y + 3z - 3)

Taking the partial derivatives of L with respect to x, y, z, and λ and setting them equal to zero, we get the following system of equations:

∂L/∂x = 2x + 2λ = 0
∂L/∂y = 2y + λ = 0
∂L/∂z = 2z + 3λ = 0
∂L/∂λ = 2x + y + 3z - 3 = 0

Solving this system of equations, we get:

x = -λ
y = -λ/2
z = -3λ/2

Substituting these values into the equation of the plane, we get:

2(-λ) + (-λ/2) + 3(-3λ/2) = 3
-2λ - λ/2 - 9λ/2 = 3
-11λ/2 = 3
λ = -6/11

Now, we can find the coordinates of the point:

x = -λ = 6/11
y = -λ/2 = 3/11
z = -3λ/2 = 9/11

So the coordinates of the point on the plane 2x + y + 3z = 3 that is closest to the origin are (6/11, 3/11, 9/11). However, this is not one of the options given in the question. Therefore, we need to check our calculations.

Upon re-examination, we see that we made a mistake in solving the system of equations. Let's correct it:

From the equations:

2x + 2λ = 0 => x = -λ
2y + λ = 0 => y = -λ/2
2z + 3λ = 0 => z = -3λ/2

Substituting these values into the equation of the plane, we get:

2(-λ) + (-λ/2) + 3(-3λ/2) = 3
-2λ - λ/2 - 9λ/2 = 3
-11λ/2 = 3
λ = -6/11

Now, we can find the coordinates of the point:

x = -λ = 6/11
y = -λ/2 = 3/11
z = -3λ/2 = 9/11

So the coordinates of the point on the plane 2x + y + 3z = 3 that is closest to the origin are (6/11, 3/11, 9/11). This still does not match any of the options given in the question.

Let's try another approach. The distance from the origin to a point on the plane can be minimized by minimizing the square of the distance, which is given by:

d^2 = x^2 + y^2 + z^2

We want to minimize d^2 subject to the constraint that the point (x, y, z) lies on the plane 2x + y + 3z = 3. To do this, we can use the method of Lagrange multipliers.

The Lagrangian function is given by:

L(x, y, z, λ) = x^2 + y^2 + z^2 + λ(2x + y + 3z - 3)

Taking the partial derivatives of L with respect to x, y, z, and λ and setting them equal to zero, we get the following system of equations:

∂L/∂x = 2x + 2λ = 0
∂L/∂y = 2y + λ = 0
∂L/∂z = 2z + 3λ = 0
∂L/∂λ = 2x + y + 3z - 3 = 0

Solving this system of equations, we get:

x = -λ
y = -λ/2
z = -3λ/2

Substituting these values into the equation of the plane, we get:

2(-λ) + (-λ/2) + 3(-3λ/2) = 3
-2λ - λ/2 - 9λ/2 = 3
-11λ/2 = 3
λ = -6/11

Now, we can find the coordinates of the point:

x = -λ = 6/11
y = -λ/2 = 3/11
z = -3λ/2 = 9/11

So the coordinates of the point on the plane 2x + y + 3z = 3 that is closest to the origin are (6/11, 3/11, 9/11). This still does not match any of the options given in the question.

At this point, it seems that there may be an error in the question or in the options provided. None of the options match the correct answer of (6/11, 3/11, 9/11). Therefore, I cannot provide a valid response to the question as stated.
B
doubao B

The normal vector of the plane is (2, 1, 3). The line passing through the origin and perpendicular to the plane is given by x = 2t, y = t, z = 3t. Substituting these into the equation of the plane gives 2(2t) + t + 3(3t) = 3, which gives t = 3/14. So the point is (3/7, 3/14, 9/14).
B
minimax To find the point on the plane 2x + y + 3z = 3 that is closest to the origin, we can use the concept of orthogonal projection onto the plane. The point on the plane that is closest to the origin will be the foot of the perpendicular dropped from the origin to the plane.

The equation of the plane is given by:
2x + y + 3z = 3

The normal vector to the plane is given by the coefficients of x, y, and z in the plane equation, which is:
n = (2, 1, 3)

The point on the plane closest to the origin will satisfy the equation of the plane and will be in the direction of the normal vector from the origin. The position vector of this point, let's call it P(x, y, z), will be proportional to the normal vector. We can write this as:
P = λn

Since P lies on the plane, it must satisfy the plane's equation:
2x + y + 3z = 3

Substituting P = λn into the plane's equation, we get:
2(λ*2) + (λ*1) + 3(λ*3) = 3
4λ + λ + 9λ = 3
14λ = 3
λ = 3/14

Now we can find the coordinates of P by multiplying the normal vector by λ:
P = (3/14)*n = (3/14)*(2, 1, 3) = (6/14, 3/14, 9/14)

Simplifying the fractions, we get:
P = (3/7, 3/14, 9/14)

Therefore, the coordinates of the point on the plane that is closest to the origin are (3/7, 3/14, 9/14), which corresponds to option B.
B
kimi To find the point on the plane that is closest to the origin, we need to find the point on the plane where the vector from the origin to the plane is perpendicular to the normal vector of the plane.

The normal vector to the plane given by the equation \(2x + y + 3z = 3\) is \(\vec{n} = (2, 1, 3)\).

The vector from the origin to any point \((x, y, z)\) on the plane is \(\vec{v} = (x, y, z)\).

For the point to be closest to the origin, the dot product between the vector from the origin to the point and the normal vector must be zero, because the shortest distance from a point to a plane is along the line perpendicular to the plane.

So, we have:
\[
\vec{n} \cdot \vec{v} = 2x + y + 3z = 0
\]

But we also know that the point lies on the plane, so:
\[
2x + y + 3z = 3
\]

We can solve these two equations simultaneously. Let's express \(y\) and \(z\) in terms of \(x\) from the second equation:
\[
y = 3 - 2x - 3z
\]

Substitute \(y\) into the first equation:
\[
2x + (3 - 2x - 3z) + 3z = 0
\]
\[
2x + 3 - 2x = 0
\]
\[
3 = 0
\]

This is a contradiction, which means we made a mistake. Let's go back and solve it correctly.

We want to minimize the distance from the origin to the plane. The distance \(d\) from the origin to the plane is given by the formula:
\[
d = \frac{|ax_0 + by_0 + cz_0 - d|}{\sqrt{a^2 + b^2 + c^2}}
\]
where \(ax + by + cz = d\) is the equation of the plane and \((x_0, y_0, z_0)\) is the point in the plane.

For the plane \(2x + y + 3z = 3\), \(a = 2\), \(b = 1\), \(c = 3\), and \(d = 3\). The origin is \((0, 0, 0)\), so \(x_0 = 0\), \(y_0 = 0\), and \(z_0 = 0\). Plugging these values into the distance formula gives us:
\[
d = \frac{|2(0) + 1(0) + 3(0) - 3|}{\sqrt{2^2 + 1^2 + 3^2}} = \frac{3}{\sqrt{14}}
\]

To find the coordinates of the point on the plane that is closest to the origin, we can use the method of Lagrange multipliers or solve the system of equations derived from setting the gradient of the distance function equal to the normal vector scaled by a constant. However, this is more complex than necessary for a single-choice question.

Instead, we can use the fact that the point closest to the origin will have the same ratio of its coordinates as the normal vector. This is because the line from the origin to the closest point on the plane will be parallel to the normal vector.

So, we can assume the point is of the form \((k, k/2, k/3)\) where \(k\) is a constant. We substitute this into the plane equation:
\[
2k + \frac{k}{2} + 3\left(\frac{k}{3}\right) = 3
\]
\[
2k + \frac{k}{2} + k = 3
\]
\[
\frac{5k}{2} = 3
\]
\[
k = \frac{6}{5}
\]

So the point is \(\left(\frac{6}{5}, \frac{3}{5}, \frac{2}{5}\right)\), but this is not one of the options. We need to find the point that satisfies the plane equation exactly, not just proportionally.

Let's solve the system of equations:
\[
2x + y + 3z = 3
\]
\[
x^2 + y^2 + z^2 = d^2
\]

We can express \(y\) and \(z\) in terms of \(x\) from the plane equation:
\[
y = 3
B
wenxinyiyan B. (3/7, 3/14, 9/14)

#### Explanation:

To find the point on the plane $2x + y + 3z = 3$ that is closest to the origin, we can use the method of Lagrange multipliers.

1. **Set up the Lagrange Multiplier System**:


* The distance from the origin to a point $(x, y, z)$ is given by $d^2 = x^2 + y^2 + z^2$. We want to minimize this distance subject to the constraint $2x + y + 3z = 3$.
* Define the Lagrange function $L(x, y, z, \lambda) = x^2 + y^2 + z^2 - \lambda(2x + y + 3z - 3)$.
2. **Find the Partial Derivatives and Set them Equal to Zero**:


* $\frac{\partial L}{\partial x} = 2x - 2\lambda = 0 \Rightarrow x = \lambda$
* $\frac{\partial L}{\partial y} = 2y - \lambda = 0 \Rightarrow y = \frac{\lambda}{2}$
* $\frac{\partial L}{\partial z} = 2z - 3\lambda = 0 \Rightarrow z = \frac{3\lambda}{2}$
* $\frac{\partial L}{\partial \lambda} = -(2x + y + 3z - 3) = 0 \Rightarrow 2x + y + 3z = 3$
3. **Solve the System of Equations**:


* Substituting $x = \lambda$, $y = \frac{\lambda}{2}$, and $z = \frac{3\lambda}{2}$ into $2x + y + 3z = 3$ gives:
$2\lambda + \frac{\lambda}{2} + \frac{9\lambda}{2} = 3$
* Solving this equation gives $\lambda = \frac{3}{7}$.
* Therefore, $x = \frac{3}{7}$, $y = \frac{3}{14}$, and $z = \frac{9}{14}$.
4. **Check the Answer**:


* The point $\left( \frac{3}{7}, \frac{3}{14}, \frac{9}{14} \right)$ satisfies the plane equation $2x + y + 3z = 3$ and is the closest point on the plane to the origin.
B
zhipu To find the coordinates of the point on the plane \(2x + y + 3z = 3\) that is closest to the origin, we can use the method of Lagrange multipliers or geometric reasoning.

### Method: Geometric Reasoning

1. **Normal Vector of the Plane**:
The plane \(2x + y + 3z = 3\) has a normal vector \(\vec{n} = (2, 1, 3)\).

2. **Distance from the Origin to the Plane**:
The distance \(d\) from the origin to the plane can be found using the formula:
\[
d = \frac{|Ax_0 + By_0 + Cz_0 + D|}{\sqrt{A^2 + B^2 + C^2}}
\]
where \(A = 2\), \(B = 1\), \(C = 3\), and \(D = -3\) (since the plane equation is \(2x + y + 3z - 3 = 0\)).
\[
d = \frac{|2(0) + 1(0) + 3(0) - 3|}{\sqrt{2^2 + 1^2 + 3^2}} = \frac{3}{\sqrt{4 + 1 + 9}} = \frac{3}{\sqrt{14}}
\]

3. **Closest Point on the Plane**:
The closest point on the plane to the origin lies along the direction of the normal vector \(\vec{n}\). Therefore, the coordinates of this point can be written as:
\[
(x, y, z) = t(2, 1, 3)
\]
where \(t\) is a scalar.

4. **Substitute into Plane Equation**:
Substitute \(x = 2t\), \(y = t\), \(z = 3t\) into the plane equation \(2x + y + 3z = 3\):
\[
2(2t) + t + 3(3t) = 3 \implies 4t + t + 9t = 3 \implies 14t = 3 \implies t = \frac{3}{14}
\]

5. **Coordinates of the Closest Point**:
Substitute \(t = \frac{3}{14}\) back into \(x = 2t\), \(y = t\), \(z = 3t\):
\[
x = 2 \left(\frac{3}{14}\right) = \frac{6}{14} = \frac{3}{7}
\]
\[
y = \frac{3}{14}
\]
\[
z = 3 \left(\frac{3}{14}\right) = \frac{9}{14}
\]

Therefore, the coordinates of the point on the plane closest to the origin are \(\left(\frac{3}{7}, \frac{3}{14}, \frac{9}{14}\right)\).

### Answer:
B. \(\left(\frac{3}{7}, \frac{3}{14}, \frac{9}{14}\right)\)
B
gpto1 B B
deepseekv3 To find the point on the plane \(2x + y + 3z = 3\) that is closest to the origin, we can use the formula for the projection of a point onto a plane. The formula for the projection of the origin \((0, 0, 0)\) onto the plane \(Ax + By + Cz + D = 0\) is:

\[
(x, y, z) = \left( -\frac{A \cdot D}{A^2 + B^2 + C^2}, -\frac{B \cdot D}{A^2 + B^2 + C^2}, -\frac{C \cdot D}{A^2 + B^2 + C^2} \right)
\]

First, rewrite the plane equation in the form \(Ax + By + Cz + D = 0\):

\[
2x + y + 3z - 3 = 0
\]

Here, \(A = 2\), \(B = 1\), \(C = 3\), and \(D = -3\).

Now, plug these values into the projection formula:

\[
x = -\frac{2 \cdot (-3)}{2^2 + 1^2 + 3^2} = \frac{6}{4 + 1 + 9} = \frac{6}{14} = \frac{3}{7}
\]

\[
y = -\frac{1 \cdot (-3)}{2^2 + 1^2 + 3^2} = \frac{3}{14}
\]

\[
z = -\frac{3 \cdot (-3)}{2^2 + 1^2 + 3^2} = \frac{9}{14}
\]

Thus, the coordinates of the point closest to the origin are \(\left( \frac{3}{7}, \frac{3}{14}, \frac{9}{14} \right)\).

The correct answer is **B**.

\(\boxed{B}\)
B