Question

已知x=1+√5，求x^3-x^2-6x+1的值

Answer 1

已知x=1+√5

x^3-x^2-6x+1

=(1+√5)^3 - (1+√5)^2 - 6(1+√5) +1

=1+2√5 +10+5√5 - (1+2√5+5)- 6 -6√5+1

=11+7√5 -6-2√5 -6 -6√5+1= - √5