∫(1-x)/(1+x^3)dx
这个就需要用因式分解
1+x^3=(1+x)(x^2-x+1)
将(1-x)化成这两个因式的加和
(1-x)=(2/3)(x^2-x+1)-(1/3)(2x-1)(x+1)
∫(1-x)/(1+x^3)dx
=∫[(2/3)(x^2-x+1)-(1/3)(2x-1)(x+1)]/(1+x^3) dx
=(2/3)∫1/(x+1)dx - (1/3) ∫[(2x^2-2x+2)+(3x-3)]/(x^2-x+1) dx
=(2/3) ln(x+1)-(2/3)x+(1/2)∫1/(x^2-x+1)d(x^2-x+1)+ (√3/3)arctan[(2x-1)/√3]
=(2/3) lnI x+1I-(2/3)x+(1/2)lnIx^2-x+1I+(√3/3)arctan[(2x-1)/√3]+C
解答完毕,请指教,真麻烦啊呀
追问你知道2x/(x^3+1)的积分怎么求吗?
追答通用的方法
2x=2(x+1)^2-2(x^2-x+1)
自己去算吧。方法类似
追问=∫[(2/3)(x^2-x+1)-(1/3)(2x-1)(x+1)]/(1+x^3) dx
=∫[(2/3)/(x+1)-(1/3)(2x-1)/(x^2-x+1)]/ dx
x^2-x+1的导数为2x-1,
=2/3ln|x+1|-1/3ln|x^2-x+1|+c 对不?
追答偶,对不住了,解错了,呵呵。该休息了
追问谢谢,嘿嘿