f(x)=x+x^(1/3)
定義域是R
f(-x)=(-x)+(-x)^(1/3)
=-(x+x^(1/3))
=-f(x)
∴f(x)是奇函數(shù)
x是增函數(shù)
x^(1/3)是增函數(shù)
∴f(x)是增函數(shù)
f(a-2)+f(1+a)≤0
f(1+a)≤-f(a-2)
∵f(x)是奇函數(shù)
∴f(1+a)≤f(2-a)
∵f(x)是增函數(shù)
∴1+a≤2-a
2a≤1
a≤1/2
a的范圍{a|a≤1/2}