Simplify each of the following and express it in the form a + ib :

Given: $(3+\sqrt{-16})-(4-\sqrt{-9})$

We re - write the above equation

$(3+\sqrt{(-1) \times 16})(-1)(4-\sqrt{(-1) \times 9})$

$=\left(3+\sqrt{16 i^{2}}\right)-\left(4-\sqrt{9 i^{2}}\right)\left[\because i^{2}=-1\right]$

$=(3+4 i)-(4-3 i)$

Now, we open the brackets, we get

$3+4 i-4+3 i$

$=-1+7 i$