Complex numbers and square root property

Im doing test corrections and need some help. My answers are wrong. Could you please show your work? Thanks.

simpify

square root of -12

I took the i out. I see that 3 and 4 go into 12. I reduced the 4 to 2. I got 3i square root of 2

square root of -16 and the square root of -49

Took the i out and got 4. Took the i out and got 7. My answer was 2i square root of 2 i square root of 7.

Divide the complex numbers

4 - 3i / 2 - 7i

I added 2 + 7i on the top. I foiled the problem. and got 8+28i - 6i - 21i^2. My answer was 29 - 22i

Solve the following equations by using the square root property.

4x^2 + 16 = 0

Thanks.