I've been trying to figure out this question but i dont know where im going wrong when i plug back in the solutions i get, i get a bunch of wacky numbers...

question : x^2 + (x + 2) ^2 = 290

my work:

= x^2 + (x +2) + (x + 2) = 290

= 2x^2 + 4x + 4 = 290

= 2x + 4x - 286 = 0

= 2 (x^2 + 2x - 143) = 0

= (x - 11) ( x + 13)

x = 11

x = -13 .. why is this wrong?