1.y =9-(2-x^2+1)^2=9-(x^2-3)^2
x^2>=3时,函数减,
x^2=0部份
令x>y>0,f(x)-f(y)=f(x)+f(-y)=f(x-y) f(x)0时为单调递减.由奇函数对称性,f(x)在R上单调递减.