Answer
$8i$
Work Step by Step
Step 1: $\sqrt {-4}+\sqrt {-36}$
Step 2: $\sqrt {-1\times4}+\sqrt {-1\times36}$
Step 3: $(\sqrt {-1}\times\sqrt 4)+(\sqrt {-1}\times\sqrt {36})$
Step 4: $(i\times\sqrt 4)+(i\times\sqrt {36})$
Step 5: $(i\times2)+(i\times6)$
Step 6: $2i+6i$
Step 7: $8i$
