Question 297402
(x+x+1)^2=x+11

(2x+1)^2=x+11

4x^2+4x+[1]=x+11 (subtract the x+11 to bring it to the other side)
[You missed the 1*1=1 term.]
4x^2+3x-[10]=0 
(4x-5)(x+2)=0
4x-5=x=5/4 not an integer.
x+2=0
x=-2 ans.
Proof:
(-2-1)^2=-2+11
-3^2=9
9=9