In Exercises 1-4, determine whether the transformation is linear.
1. $T(M) = M \begin{bmatrix} 1 & 2 \ 3 & 6 \end{bmatrix}$ from $\mathbb{R}^{2 \times 2}$ to $\mathbb{R}^{2 \times 2}$
2. $T(M) = PMP^{-1}$, where $P = \begin{bmatrix} 2 & 3 \ 5 & 7 \end{bmatrix}$, from $\mathbb{R}^{2 \times 2}$ to $\mathbb{R}^{2 \times 2}$
3. $T(x + iy) = x - iy$ from $\mathbb{C}$ to $\mathbb{C}$
4. $T(f(t)) = \int_{-2}^{3} f(t) dt$ from $P_2$ to $\mathbb{R}$
