Question

1.当x^2-2x-1=0,求代数式x^4-x^3-3x^2-x+5的值.

Answer 1

x^4-x^3-3x^2-x+5

=x^4-2x^3-x^2+x^3-2x^2-x+5

=x^2(x^2-2x-1)+x(x^2-2x-1)+5

=0+0+5

=5