Question

若f（√x+1）=x-2√x，则f（x）的解斥式为

求解释过程
题打错了应是f（√x+1）=x+√2

Answer 1

令a=√x+1
√x=a-1
x=(a-1)²
所以f(a)=(a-1)²-2(a-1)=a²-4a+3
f(x)=x²-4x+3

Answer 2

f（√x+1）=x+√2
=（√x+1)²-2√x+√2-1
=(√x+1)²-2(√x+1)+√2+1

f(x)=x²-2x+√2+1