(x)为一次函数设f(x)=kx+bf(f(x))=1+2xf(kx+b)=1+2xk(kx+b)+b=1+2x(k^2-2)x+bk+b-1=0对所有的x都满足,所有k^2-2=0kb+b-1=0k=根号2,b=根号2-1k=-根号2,b=-根号2-1f(x)=根号2x+根号2-1或者f(x)=-根号2x-根号2-1
