Solving problems in simplest form
I know the answer to some of these, and the others I'm not sure of. Can you please explain to me how I can work them out in simplest form?
1) (-5 - √-9^2) answer is 30 + 16i?
2) x^2 + 5x + 2 = 0 answer is {-5 + √17 / 2, -5 - √17 / 2
3) √6x + 1 = x - 1 answer is {0, 8}?
4) 2x + 5 <17 answer is x<6?
5) 3x^2 - 1 = 47 answer is {-4, 4}
6) x^2 - 2x + 17 = 0 answer is {1 + 4i, 1 - 4i)
7) 4x^3 - 12x^2 = 9x - 27 answer is { -3/2, 3, 3/2}
8) |x| = 6 answer is {6}?
9) √x + 10 = x - 2 answer is {-1}?
10) (-7 + 5i) - (-9 -11i) answer is 2 + 16i
11) (2 + 7i) ( 2 - 7i) answer is 4 - 49i
12) √-81 - √-144 answer is -3
13) Solve x^2 - 13x + 36 = 0 answer is {4, 9}
14) Solve 5x^2 - 20x = 0 answer is {0, 4}