x2=x+1
x^5-5x+6
=x(x+1)^2-5x+6
=x^3+2x^2+x-5x+6
=x(x+1)+2(x+1)-4x+6
=x^2+x+2x+2-4x+6
=x^2-x+8
=x+1-x+8
=9