Question

已知x的二次方减3x减1=0,求代数式2x的三次方减3x的二次方减11x加8的值

Answer 1

x^2-3x-1=0

2x^3-3x^2-11x+8

=(2x^3-6x^2-2x)+(3x^2-9x-3)+11

=2x(x^2-3x-1)+3(x^2-3x-1)+11

=0+0+11

=11