Question

3x + 6 = √(-17x − 4)

Answer 1

Square both sides to remove the radical on the right side. Then you have
(3x + 6)^2 = -17x -4
and can simplify quite easily from there

Answer 2

8x=40

Answer 3

x=5

Answer 4

I think you made a mistake. the result of moving everything to one side will be a polynomial. I got
9x^2 + 53x + 40

We can still find solutions though. Do you know what the Quadratic Equation is?