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

(x+1)²+x+1=(x+1)(x+2)⇒(x+1)²+(x+1)-(x+1)(x+2)=0⇒ (x+1)(x+1+1-x-2)=0⇒x+1=0⇒x=-1