Target Exam

CUET

Subject

-- Applied Mathematics - Section B2

Chapter

Algebra

Question:

If $\left[\begin{array}{ccc}3 & 2 x+5 y & -2 \\ x+4 y & 7 & -5\end{array}\right]=\left[\begin{array}{rrr}3 & 10 & -2 \\ 2 & 7 & -5\end{array}\right]$. Then the values of x and y are:

Options:

$x=-2, y=6$

$x=12, y=5$

$x=-4, y=7$

$x=10, y=-2$

Correct Answer:

$x=10, y=-2$

Explanation:

The correct answer is Option (4) - $x=10, y=-2$

$\begin{bmatrix} 3 & 2x+5y & -2 \\ x+4y & 7 & -5 \end{bmatrix} = \begin{bmatrix} 3 & 10 & -2 \\ 2 & 7 & -5 \end{bmatrix}$

$2x + 5y = 10$

$x + 4y = 2$

$x = 2 - 4y$

$2(2 - 4y) + 5y = 10$

$4 - 8y + 5y = 10$

$4 - 3y = 10$

$-3y = 6 \Rightarrow y = -2$

$x = 2 - 4(-2) = 2 + 8 = 10$

The values are $x = 10,\; y = -2$.