f(x+1)+f(x-1)=2x^2-4x,求f(1-√2)
设f(x)=ax^2+bx+c
f(x+1)+f(x-1)=2ax^2+2bx+2c+2a=2x^2-4x
a=1,b=-2,c=-1
f(x)=x^2-2x-1=(x-1)^2-2
f(1-√2)=0