a^2+a=1,a+1=1/a,a^2+1=2-aa^5-5a+2=a.a^4-a-4a+2=a.(a^4-1)-4a+2=a.(a^2+1)(a^2-1)-4a+2=a.(2-a)(a+1)(a-1)-4a+2=a.(2-a)(1/a)(a-1)-4a+2=(2-a)(a-1)-4a+2=2a-2-a^2+a-4a+2=-(a^2+a)=-1