Compute the matrix exponential $e^{tA}$ for the matrix $A = \left[\begin{array}{cc} -7 &-5\cr 10 &8 \end{array}\right]$. Note the $t$!

$e^{tA} = {}$ $\left[\Rule{0pt}{2.4em}{0pt}\right.$$\left]\Rule{0pt}{2.4em}{0pt}\right.$