Question 93 of 480
Solve the equations
m2 + n2 = 29
m + n = 7
- A. (2, 3) and ( 3, 5)
- B. (2, 5) and (5, 2)
- C. (5, 2) and ( 5, 3)
- D. (5, 3) and (3, 5)
Correct Answer:
B
Explanation
To solve the equations given:
1. **Equations**:
- \( m^2 + n^2 = 29 \) (Equation 1)
- \( m + n = 7 \) (Equation 2)
We need to find the values of \( m \) and \( n \) that satisfy both equations.
### Step 1: Express one variable in terms of the other
From Equation 2, we can express \( n \) in terms of \( m \):
\[
n = 7 - m
\]
### Step 2: Substitute into the first equation
Now, we substitute \( n \) into Equation 1:
\[
m^2 + (7 - m)^2 = 29
\]
### Step 3: Expand the equation
Expanding \( (7 - m)^2 \):
\[
(7 - m)^2 = 49 - 14m + m^2
\]
Now substitute this back into the equation:
\[
m^2 + (49 - 14m + m^2) = 29
\]
Combine like terms:
\[
2m^2 - 14m + 49 = 29
\]
### Step 4: Simplify the equation
Subtract 29 from both sides:
\[
2m^2 - 14m + 20 = 0
\]
### Step 5: Divide the entire equation by 2
To simplify, divide everything by 2:
\[
m^2 - 7m + 10 = 0
\]
### Step 6: Factor the quadratic equation
Now we need to factor the quadratic:
\[
(m - 5)(m - 2) = 0
\]
Setting each factor to zero gives us:
\[
m - 5 = 0 \quad \Rightarrow \quad m = 5
\]
\[
m - 2 = 0 \quad \Rightarrow \quad m = 2
\]
### Step 7: Find corresponding values of \( n \)
Now we can find the corresponding values of \( n \) using \( n = 7 - m \):
- If \( m = 5 \):
\[
n = 7 - 5 = 2 \quad \Rightarrow \quad (m, n) = (5, 2)
\]
- If \( m = 2 \):
\[
n = 7 - 2 = 5 \quad \Rightarrow \quad (m, n) = (2, 5)
\]
### Step 8: List the solutions
Thus, the pairs \( (m, n) \) that satisfy both equations are:
- \( (5, 2) \)
- \( (2, 5) \)
### Step 9: Evaluate the options
Now, let's evaluate the options provided:
- **A. (2, 3) and (3, 5)**: Incorrect, as neither pair satisfies both equations.
- **B. (2, 5) and (5, 2)**: Correct, as both pairs satisfy the equations.
- **C. (5, 2) and (5, 3)**: Incorrect, as (5, 3) does not satisfy the first equation.
- **D. (5, 3) and (3, 5)**: Incorrect, as neither pair satisfies both equations.
### Conclusion
The correct option is **B. (2, 5) and (5, 2)**.
### Revision Summary
- To solve simultaneous equations, express one variable in terms of the other and substitute.
- Expand and simplify the equations to form a quadratic equation.
- Factor the quadratic to find the values of the variables.
- Verify the solutions against the original equations to ensure they are correct.