Question

x²-3x=1=0求代数式2x³-3x²-11x+8

Answer 1

x²－3x=1 ===>>> x²=3x＋1

2x³－3x²－11x＋8

=2x(3x＋1)－3(3x＋1)－11x＋8 ====>>>>> x²=3x＋1

=6x²－18x－1

=6(x²－3x)－1 ======>>>> x²－3x=1

=5