Question

已知x的平方-2x-1=0,求x的4次方-12x

Answer 1

x的平方-2x-1=0

x²-1=2x

x-1/x=2

(x-1/x)²=2²

x²-2+1/x²=4

x²+1/x²=6

(x²+1/x²)²=6²

x^4+2+1/x^4=36

x^4+1/x^4=34