If $\begin{bmatrix} a + b & 2 \ 5 & ab \end{bmatrix} = \begin{bmatrix} 6 & 2 \ 5 & 8 \end{bmatrix}$, then the values of a and b are:

1. a = 4, b = 2

2. a = 2, b = 4

3. both (a) and (b)

4. none of these

If A = $\begin{bmatrix} 0 & -1 & 2 \ 1 & 0 & 3 \ -2 & -3 & 0 \end{bmatrix}$, then (A + A′) is equal to :

1. 0

2. 2A

3. –A′

4. A′

If $x\begin{bmatrix} 2 \ 1 \end{bmatrix} + y\begin{bmatrix} 3 \ 5 \end{bmatrix} + \begin{bmatrix} -8 \ -11 \end{bmatrix}$ = 0, then the value of (2x – 3y) is:

1. 1

2. -4

3. 3

4. -3

If $\begin{bmatrix} 2 & 3 \ -4 & 1 \end{bmatrix} + 2A = 4 \begin{bmatrix} -1 & 2 \ 3 & 4 \end{bmatrix}$, then the matrix A is:

1. $\begin{bmatrix} -3 & 5 \ 8 & 15 \end{bmatrix}$

2. $\begin{bmatrix} 5 & -3 \ 15 & 8 \end{bmatrix}$

3. $\begin{bmatrix} -3 & \dfrac{5}{2} \ 8 & \dfrac{15}{2} \end{bmatrix}$

4. $\begin{bmatrix} \dfrac{5}{2} & -3 \ \dfrac{15}{2} & 8 \end{bmatrix}$