Question

已知f(x+x/1)=x3+x3/1,求f(x) x3是x的三次方 配凑法

Answer 1

f(x+1/x)=x3+1/x3=(x+1/x)(x²-1+1/x²)=(x+1/x){(x+1/x)²-3}

f(x)=x(x²-3)=x^3-3x