integral of 1/(x^8+x^6)

解

\int \frac{1}{x ^{8} + x ^{6}} d x

- \frac{1}{x} + \frac{1}{3 x ^{3}} - \frac{1}{5 x ^{5}} - arctan (x) + C

解答ステップ

\int \frac{1}{x ^{8} + x ^{6}} d x

以下の部分分数を得る:

\frac{1}{x ^{8} + x ^{6}} : \frac{1}{x ^{2}} - \frac{1}{x ^{4}} + \frac{1}{x ^{6}} - \frac{1}{x ^{2} + 1}

= \int \frac{1}{x ^{2}} - \frac{1}{x ^{4}} + \frac{1}{x ^{6}} - \frac{1}{x ^{2} + 1} d x

総和規則を適用する:

\int f (x) \pm g (x) d x = \int f (x) d x \pm \int g (x) d x

= \int \frac{1}{x ^{2}} d x - \int \frac{1}{x ^{4}} d x + \int \frac{1}{x ^{6}} d x - \int \frac{1}{x ^{2} + 1} d x

\int \frac{1}{x ^{2}} d x = - \frac{1}{x}

\int \frac{1}{x ^{4}} d x = - \frac{1}{3 x ^{3}}

\int \frac{1}{x ^{6}} d x = - \frac{1}{5 x ^{5}}

\int \frac{1}{x ^{2} + 1} d x = arctan (x)

= - \frac{1}{x} - (- \frac{1}{3 x ^{3}}) - \frac{1}{5 x ^{5}} - arctan (x)

簡素化

= - \frac{1}{x} + \frac{1}{3 x ^{3}} - \frac{1}{5 x ^{5}} - arctan (x)

定数を解答に追加する

= - \frac{1}{x} + \frac{1}{3 x ^{3}} - \frac{1}{5 x ^{5}} - arctan (x) + C