Are the following matrices invertible?

Choose Invertible Not invertible  1. $\left[\begin{array}{cc} -2 &2\cr 6 &-6 \end{array}\right]$

Choose Invertible Not invertible  2. $\left[\begin{array}{cc} 5 &0\cr -3 &2 \end{array}\right]$

Choose Invertible Not invertible  3. $\left[\begin{array}{cc} -3 &1\cr -3 &3 \end{array}\right]$

Choose Invertible Not invertible  4. $\left[\begin{array}{cc} 6 &2\cr 0 &0 \end{array}\right]$