问题


There is a single choice question about high school mathematics. Answer the question by replying A, B, C or D.
Question: If $725x + 727y = 1500$ and $729x+ 731y = 1508$, what is the value of $x - y$ ?
A. 725
B. -2
C. 2
D. -48
Answer:

答案

模型 模型答案 正确答案
金声玉亮2.0 To solve this system of equations, we can subtract the first equation from the second to eliminate the constants on the right side. This gives us:

$$(729x + 731y) - (725x + 727y) = 1508 - 1500$$

Simplifying both sides:

$$4x + 4y = 8$$

Dividing by 4:

$$x + y = 2$$

Now, we need to find $x - y$. We can manipulate the original equations to find this. Let's multiply the first equation by 731 and the second by 727, then subtract the second from the first:

$$731(725x + 727y) - 727(729x + 731y) = 731(1500) - 727(1508)$$

Simplifying:

$$521225x + 531997y - 528283x - 530037y = 1096500 - 1085176$$

$$2942x - 1040y = 11324$$

Dividing by 2:

$$1471x - 520y = 5662$$

Now, we can use the equation $x + y = 2$ to solve for $x$ and $y$. Let's multiply this equation by 520 and subtract it from the equation we just derived:

$$1471x - 520y - 520(x + y) = 5662 - 520(2)$$

$$1471x - 520x - 520y - 520y = 5662 - 1040$$

$$951x - 1040y = 4622$$

Now, we can solve for $x$ and $y$ using the two equations:

1. $x + y = 2$
2. $951x - 1040y = 4622$

Multiplying the first equation by 951:

$$951x + 951y = 1902$$

Subtracting this from the second equation:

$$951x - 1040y - (951x + 951y) = 4622 - 1902$$

$$-1991y = 2720$$

$$y = -\frac{2720}{1991} = -\frac{80}{57}$$

Substituting $y$ back into $x + y = 2$:

$$x - \frac{80}{57} = 2$$

$$x = 2 + \frac{80}{57} = \frac{114 + 80}{57} = \frac{194}{57}$$

Now, we can find $x - y$:

$$x - y = \frac{194}{57} - (-\frac{80}{57}) = \frac{194 + 80}{57} = \frac{274}{57} = 4\frac{50}{57}$$

However, this is not one of the options. Let's re-evaluate the simplification process. The key is to find $x - y$ directly from the given equations without solving for $x$ and $y$ individually. We already found $x + y = 2$. Let's subtract twice this equation from the second original equation:

$$729x + 731y - 2(x + y) = 1508 - 2(2)$$

$$729x + 731y - 2x - 2y = 1504$$

$$727x + 729y = 1504$$

This is very similar to the first equation, $725x + 727y = 1500$. Subtracting the first equation from this new equation:

$$(727x + 729y) - (725x + 727y) = 1504 - 1500$$

$$2x + 2y = 4$$

Dividing by 2:

$$x + y = 2$$

This is the same equation we found earlier. However, we need $x - y$. Let's subtract the first original equation from the second:

$$(729x + 731y) - (725x + 727y) = 1508 - 1500$$

$$4x + 4y = 8$$

Dividing by 4:

$$x + y = 2$$

This is not directly helpful for finding $x - y$. Let's try a different approach. We can subtract the first equation from the second to eliminate the constants:

$$729x + 731y - (725x + 727y) = 1508 - 1500$$

$$4x + 4y = 8$$

Dividing by 4:

$$x + y = 2$$

Now, let's subtract twice this equation from the second original equation:

$$729x + 731y - 2(x + y) = 1508 - 2(2)$$

$$729x + 731y - 2x - 2y = 1504$$

$$727x + 729y = 1504$$

Subtracting the first original equation from this new equation:

$$(727x + 729y) - (725x + 727y) = 1504 - 1500$$

$$2x + 2y = 4$$

Dividing by 2:

$$x + y = 2$$

This is not directly helpful for finding $x - y$. Let's try a different approach. We can subtract the first equation from the second to eliminate the constants:

$$729x + 731y - (725x + 727y) = 1508 - 1500$$

$$4x + 4y = 8$$

Dividing by 4:

$$x + y = 2$$

Now, let's subtract the first equation from the second equation again, but this time we'll subtract the equation $x + y = 2$ multiplied by 725 from the first original equation and the equation $x + y = 2$ multiplied by 729 from the second original equation:

$$(725x + 727y) - 725(x + y) = 1500 - 725(2)$$

$$(729x + 731y) - 729(x + y) = 1508 - 729(2)$$

Simplifying:

$$2y = 4$$

$$2x = 8$$

Dividing by 2:

$$y = 2$$

$$x = 4$$

Now, we can find $x - y$:

$$x - y = 4 - 2 = 2$$

The correct answer is:

C. 2
D
deepseekr1

To solve the system of equations:

1. \(725x + 727y = 1500\)
2. \(729x + 731y = 1508\)

**Step 1:** Subtract the first equation from the second to eliminate constants:
\[
(729x - 725x) + (731y - 727y) = 1508 - 1500
\]
Simplifying:
\[
4x + 4y = 8 \implies x + y = 2 \quad \text{(Equation 3)}
\]

**Step 2:** Substitute \(y = 2 - x\) into the first equation:
\[
725x + 727(2 - x) = 1500
\]
Expanding and simplifying:
\[
725x + 1454 - 727x = 1500 \implies -2x = 46 \implies x = -23
\]
Then, \(y = 2 - (-23) = 25\).

**Step 3:** Calculate \(x - y\):
\[
x - y = -23 - 25 = -48
\]

**Verification:** Substituting \(x = -23\) and \(y = 25\) into both original equations confirms the solution is correct.

**Answer:** \(\boxed{D}\)
D
gpto1 D D
GPT-4o To solve for \( x - y \) from the given equations, we can use the method of elimination.

Given:
\[ 725x + 727y = 1500 \quad \text{(1)} \]
\[ 729x + 731y = 1508 \quad \text{(2)} \]

First, subtract equation (1) from equation (2):
\[ (729x + 731y) - (725x + 727y) = 1508 - 1500 \]
\[ 4x + 4y = 8 \]
\[ x + y = 2 \quad \text{(3)} \]

We have the new equation:
\[ x + y = 2 \]

Next, we solve the system of equations:
Equations (1) and (3):
\[ 725x + 727y = 1500 \quad \text{(1)} \]
\[ x + y = 2 \quad \text{(3)} \]

From equation (3):
\[ y = 2 - x \]

Substitute \( y = 2 - x \) into equation (1):
\[ 725x + 727(2 - x) = 1500 \]
\[ 725x + 1454 - 727x = 1500 \]
\[ -2x + 1454 = 1500 \]
\[ -2x = 1500 - 1454 \]
\[ -2x = 46 \]
\[ x = -23 \]

Since \( y = 2 - x \):
\[ y = 2 - (-23) \]
\[ y = 25 \]

Finally, calculate \( x - y \):
\[ x - y = -23 - 25 \]
\[ x - y = -48 \]

Therefore, the value of \( x - y \) is:
\[ \boxed{-48} \]

The correct answer is:
D. -48
D
llama3.1-70B-Instruct

B
D
llama3.1-405B-Instruct

To solve this system of equations, we can use the method of elimination. First, let's subtract the first equation from the second equation to eliminate the variable y:

(729x + 731y) - (725x + 727y) = 1508 - 1500

This simplifies to:

4x + 4y = 8

Now, we can divide both sides of the equation by 4 to get:

x + y = 2

Now, we can solve for x in terms of y:

x = 2 - y

Now, we can substitute this expression for x into one of the original equations. Let's use the first equation:

725x + 727y = 1500

Substituting x = 2 - y, we get:

725(2 - y) + 727y = 1500

Expanding and simplifying, we get:

1450 - 725y + 727y = 1500

Combine like terms:

2y = 50

Divide both sides by 2:

y = 25

Now that we have found y, we can find x:

x = 2 - y
x = 2 - 25
x = -23

Now, we can find the value of x - y:

x - y = -23 - 25
x - y = -48

So, the value of x - y is -48.

The best answer is D.
D
DeepSeek-Coder-V2 B. -2 D
Qwen2-72B-Instruct To solve this problem, we can use the method of elimination or substitution. However, in this case, the elimination method might be quicker.

Given the equations:
1) $725x + 727y = 1500$
2) $729x + 731y = 1508$

We can subtract the first equation from the second equation to eliminate $y$:

$(729x + 731y) - (725x + 727y) = 1508 - 1500$

This simplifies to:

$4x + 4y = 8$

Dividing the entire equation by 4:

$x + y = 2$

However, we need to find the value of $x - y$. We can manipulate the equation we just found to help us solve for it. We can add $2y$ to both sides of the equation $x + y = 2$ and then subtract $2y$ from the right side to get:

$x + y + 2y = 2 + 2y$

$x + 3y = 2 + 2y$

Subtracting $3y$ from both sides:

$x = 2 - y$

Now subtract $y$ from both sides to get $x - y$:

$x - y = 2 - 2y$

We still need the value of $y$ to find $x - y$. We can use the equation $x + y = 2$ to solve for $y$. We can subtract $x$ from both sides:

$x + y - x = 2 - x$

$y = 2 - x$

Plugging this value of $y$ into $x - y = 2 - 2y$:

$x - (2 - x) = 2 - 2(2 - x)$

$x - 2 + x = 2 - 4 + 2x$

$2x - 2 = 2x - 2$

This doesn't directly give us the value of $x - y$, but we can see that we made an algebraic error in our attempt to isolate $y$. Let's go back to $x + y = 2$ and solve for $y$ again:

$x + y = 2$

$y = 2 - x$

Now, let's plug this value of $y$ into one of the original equations to solve for $x$. We can use the first equation:

$725x + 727(2 - x) = 1500$

$725x + 1454 - 727x = 1500$

$-2x = 1500 - 1454$

$-2x = 46$

$x = -23$

Now that we have $x$, we can find $y$:

$x + y = 2$

$-23 + y = 2$

$y = 2 + 23$

$y = 25$

Finally, we can find $x - y$:

$x - y = -23 - 25$

$x - y = -48$

So, the answer is D. -48.
D
baichuan4 C D
doubao Subtracting the first equation from the second equation gives:

$(729x+731y)-(725x+727y)=1508-1500$

$729x+731y-725x-727y=8$

$4x+4y=8$

$x+y=2$.

Multiplying the first equation by 731 and the second equation by 727, then subtracting:

$731(725x+727y)-727(729x+731y)=731\times1500-727\times1508$

$731\times725x+731\times727y-727\times729x-727\times731y=1096500-1095416$

$731\times725x-727\times729x=1084$

$x(731\times725-727\times729)=1084$

$x=\frac{1084}{731\times725-727\times729}$.

Multiplying the first equation by 729 and the second equation by 725, then subtracting:

$729(725x+727y)-725(729x+731y)=729\times1500-725\times1508$

$729\times725x+729\times727y-725\times729x-725\times731y=1093500-1091000$

$729\times727y-725\times731y=2500$

$y(729\times727-725\times731)=2500$

$y=\frac{2500}{729\times727-725\times731}$.

Then $x-y=\frac{1084}{731\times725-727\times729}-\frac{2500}{729\times727-725\times731}=-2$.

So the answer is B.
D
minimax To find the value of $x - y$, we can solve the system of equations given:

\[
\begin{align*}
725x + 727y &= 1500 \quad \text{(1)} \\
729x + 731y &= 1508 \quad \text{(2)}
\end{align*}
\]

We can subtract equation (1) from equation (2) to eliminate $y$:

\[
\begin{align*}
(729x + 731y) - (725x + 727y) &= 1508 - 1500 \\
729x - 725x + 731y - 727y &= 8 \\
4x + 4y &= 8 \\
x + y &= 2 \quad \text{(3)}
\end{align*}
\]

Now, we can multiply equation (3) by 727 to make the coefficient of $y$ the same as in equation (1):

\[
\begin{align*}
727(x + y) &= 727 \cdot 2 \\
727x + 727y &= 1454 \quad \text{(4)}
\end{align*}
\]

Subtract equation (4) from equation (1):

\[
\begin{align*}
(725x + 727y) - (727x + 727y) &= 1500 - 1454 \\
725x - 727x &= 46 \\
-2x &= 46 \\
x &= -23
\end{align*}
\]

Now we can substitute $x = -23$ into equation (3) to find $y$:

\[
\begin{align*}
-23 + y &= 2 \\
y &= 2 + 23 \\
y &= 25
\end{align*}
\]

Finally, we can find $x - y$:

\[
\begin{align*}
x - y &= -23 - 25 \\
x - y &= -48
\end{align*}
\]

So the value of $x - y$ is $-48$, which corresponds to answer choice D.
D
kimi To solve this problem, we can use the method of elimination to find the value of \( x - y \). We have two equations:

1) \( 725x + 727y = 1500 \)
2) \( 729x + 731y = 1508 \)

We can subtract equation 1 from equation 2 to eliminate \( y \):

\( (729x + 731y) - (725x + 727y) = 1508 - 1500 \)

This simplifies to:

\( 4x + 4y = 8 \)

Now, we can simplify this equation by dividing both sides by 4:

\( x + y = 2 \)

Now, we want to find \( x - y \). We can use the original equations to find another expression involving \( x - y \). Let's subtract equation 1 from equation 2 again, but this time we will rearrange the terms to isolate \( x - y \):

\( 729x - 725x + 731y - 727y = 1508 - 1500 \)

This simplifies to:

\( 4x - 4y = 8 \)

Now, we can simplify this equation by dividing both sides by 4:

\( x - y = 2 \)

So, the value of \( x - y \) is 2, which corresponds to option C.

Answer: C. 2
D
wenxinyiyan B

Explanation:
Subtracting the first equation from the second, we get:

$\begin{align*}
(729x - 725x) + (731y - 727y) = 1508 - 1500 \n4x + 4y = 8 \nx + y = 2 \quad (1)
\end{align*}$

Next, we rearrange the first equation to express $x$ in terms of $y$:

$\begin{align*}
725x = 1500 - 727y \nx = \frac{1500 - 727y}{725} \quad (2)
\end{align*}$

Substituting (2) into (1), we get:

$\begin{align*}
\frac{1500 - 727y}{725} + y = 2 \n1500 - 727y + 725y = 1450 \n-2y = -50 \ny = 25
\end{align*}$

Using the value of $y$ in (2), we can find $x$:

$\begin{align*}
x = \frac{1500 - 727 \times 25}{725} \nx = \frac{1500 - 18175}{725} \nx = \frac{-16675}{725} \nx = -23
\end{align*}$

Finally, we calculate $x - y$:

$\begin{align*}
x - y = -23 - 25 \nx - y = -48
\end{align*}$
D
zhipu To find the value of \( x - y \), let's start by writing down the given equations:

\[
725x + 727y = 1500 \quad \text{(1)}
\]
\[
729x + 731y = 1508 \quad \text{(2)}
\]

First, we'll subtract equation (1) from equation (2):

\[
(729x + 731y) - (725x + 727y) = 1508 - 1500
\]

This simplifies to:

\[
729x - 725x + 731y - 727y = 8
\]

Further simplification gives:

\[
4x + 4y = 8
\]

Divide both sides by 4:

\[
x + y = 2 \quad \text{(3)}
\]

Next, we need another equation to solve for \( x \) and \( y \). Let's multiply equation (3) by 727:

\[
727(x + y) = 727 \cdot 2
\]

This simplifies to:

\[
727x + 727y = 1454 \quad \text{(4)}
\]

Now, subtract equation (4) from equation (1):

\[
(725x + 727y) - (727x + 727y) = 1500 - 1454
\]

This simplifies to:

\[
725x - 727x = 46
\]

\[
-2x = 46
\]

Solving for \( x \):

\[
x = -23
\]

Now, substitute \( x = -23 \) into equation (3):

\[
-23 + y = 2
\]

Solving for \( y \):

\[
y = 25
\]

Finally, we find \( x - y \):

\[
x - y = -23 - 25 = -48
\]

Thus, the value of \( x - y \) is:

\[
\boxed{-48}
\]

So, the correct answer is:

D. -48
D
gpto1 D D
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