Question 788159
(a,8) is a point on the graph y=x^2+2x, what is a?

plug x=a and y=8

since (a,8) satisfies the equation 

8=a^2+2a

a^2+2a-8=0

a^2+4a-2a-8=0

a(a+4)-2(a+4)=0

(a+4)(a-2)=0

a=-4 OR 2