(1)
f(-1)=-f(a)
-1-2a+a^2=-(-a^2+2a^2+a^2)
求根a=1 a=-1/3(舍)
即:f(x)=-x^2+2x+1
(2)
f(x)=-(x-1)^2+2
当x=1时f(x)最大,f(x)最大值为2