If x and y are two real numbers such that 3x + 2y = 5 and 5x + 4y = 9, then 4x + 3y =?
A. 1
B. 2
C. 5
D. 6
E. 7
Correct Answer: E
Explanation
To find the value of \(4x + 3y\) given the equations:
1. \(3x + 2y = 5\)
2. \(5x + 4y = 9\)
we can solve this system of linear equations. Here’s the step-by-step method:
Step 1: Solve the System of Equations
Equation 1:
\[
3x + 2y = 5
\]
Equation 2:
\[
5x + 4y = 9
\]
To eliminate one of the variables, we can multiply Equation 1 by 2 to align the coefficients of \(y\):
\[
2 \times (3x + 2y) = 2 \times 5
\]
\[
6x + 4y = 10
\]
Now subtract Equation 2 from this result:
\[
(6x + 4y) - (5x + 4y) = 10 - 9
\]
\[
x = 1
\]
Step 2: Substitute \(x = 1\) into Equation 1 to find \(y\):
Substitute \(x = 1\) into Equation 1:
\[
3(1) + 2y = 5
\]
\[
3 + 2y = 5
\]
\[
2y = 2
\]
\[
y = 1
\]
Step 3: Calculate \(4x + 3y\) using \(x = 1\) and \(y = 1\):
\[
4x + 3y = 4(1) + 3(1) = 4 + 3 = 7
\]
The value of \(4x + 3y\) is 7
The correct answer is E. 7