$\cosθ \cdot \begin{bmatrix} \cosθ & \sinθ \ -\sinθ & \cosθ \end{bmatrix} + \sinθ \cdot \begin{bmatrix} \sinθ & -\cosθ \ \cosθ & \sinθ \end{bmatrix}$ is equal to:

1. $\begin{bmatrix} 1 & 1 \ 1 & 1 \end{bmatrix}$

2. $\begin{bmatrix} 0 & 1 \ 1 & 0 \end{bmatrix}$

3. $\begin{bmatrix} 1 & 0 \ 0 & 1 \end{bmatrix}$

4. none of these

If $2\begin{bmatrix} 3 & 4 \ 5 & x \end{bmatrix} + \begin{bmatrix} 1 & y \ 0 & 1 \end{bmatrix} = \begin{bmatrix} 7 & 0 \ 10 & 5 \end{bmatrix}$, then the value of (x – y) is:

1. 10

2. -10

3. 6

4. -6

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′