Question

一道基本数学函数题已知f(x^1/2+1)=x+2x^1/2,求f(x).

Answer 1

x^1/2 就是√x 咯

f(√x+1)=x+2√x

令t=√x+1 那么x =(t-1)^2

f(t) =(t-1)^2 +2(t-1)

也就是f(x)=(x-1)^2 +2(x-1)=x^2-1