a^2+(a+1)^2+(a^2+a)^2
=a^2+(a+1)^2+a^2(a+1)^2
=a^2+(a+1)^2+2a(a+1)-2a(a+1)+a^2(a+1)^2
=(a+1-a)^2+(a2+a)^2 +2a(a+1)
=1+2a(a+1)+(a2+a)^2
=(a2+a+1)^2