f(x)+2f(-x)=x²+2x,求f(x)的解析式= =

f(x)+2f(-x)=x²+2x,求f(x)的解析式= =
f(x)+2f(-x)=x²+2x,求f(x)的解析式
= =

f(x)+2f(-x)=x²+2x,求f(x)的解析式= =
f(-x)+2f(x)=x^2-2x
3f(-x)+3f(x)=2x^2
3f(-x)+6f(x)=3x^2-6x
3f(x)=x^2-6x
f(x)=x^2/3-2x