Evaluate the following expressions and write them in the form $a + b i$.

$9 + \sqrt{-36} =$ .

$\sqrt{-9} \sqrt{-36} =$ .

$\displaystyle \frac{9}{ \sqrt{-1} } =$ .

$\displaystyle \frac{ \sqrt{-1} }{ \sqrt{-1} \sqrt{-9} } =$ . (Note: enter $a$ and $b$ using decimal approximations, not fractions.)

$-8 (3 + \sqrt{-36}) =$ .