X2 plus 2X equals 8 completing the square?

Answer 1

I think this is how you do it:

x2+2x = 8

x2+2x+(1/2*(2))2 = 8 + (1/2*(2))2

x2+2x+1=8+1

(x+1)2 = 9

SQ.ROOT [(x+1)2 = 9]

x+1 = 3 and x+1 = -3

so,

x=2 and x=-4