AP ICET 2018 Question Paper Shift-2 (2nd May)

Question 127

If $$\begin{bmatrix}3 & -2 \\-1 & 2 \end{bmatrix}\begin{bmatrix}x\\y \end{bmatrix} = \begin{bmatrix}11 \\-5 \end{bmatrix}$$ then 3x + 7y = 

Solution

Multiplying the matrices on the LHS and equating with the one on RHS, we get:
3x - 2y = 11
-x + 2y = -5

Adding the 2 equations, we get x = 3, y = -1

Hence, 3x - 7y = 9-7 = 2

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