当x=0时,
f(-0)= -f(0)
f(0)= - f(0)
f(0)=0
当x0
f(-x)= - (-x)^2+2x+2
= - x^2+2x+2
因为f(x)是奇函数,所以,f(-x)= - f(x)
-f(x)= - x^2+2x+2
f(x)=x^2-2x-2
` {x^2-2x-2 (x0)