Imaginary (Complex) Number Question

I need help solving this.
-2(x+1)^2=72
I think the answer is x=7i or x=-7i, but I am unsure.
I get as far as x + 1= -6, but I am unsure as to what to do to the +1.

Ok so, start by dividing both sides by -2, so you get (x+1)^2 = -36. Then, square root both sides and you get x+1 = 6i.

The reason the ride side of the equation is 6i and not just 6 is because when you divided +72 by -2, you got -36. Then, you took the square root of -36. When you take the square root of a negative number, you will always get an "i". Therefore, because the square root of 36 is 6 and 36 was a negative number, the right side of the equation is 6i.

Now, just simply subtract 1 from both sides and your answer is x= 6i-1.

foil out (x+1)^2

-2(x^2+2x+1)=72

divide the whole equation by -2

x^2+2x+1=-36

then factor

(x+1)^2=-36

square root both sides

x+1 =+or - 6i

x= -1+6i
x= -1-6i

Your Welcome
:)

(x+1)^2= -36 so x+1 = +- 6i and x=- 1+6i and x = -1-6i

x+1=-6
-1 -1

x = -7