integral of 1/(x^3(x+2)^3)

解答

\int \frac{1}{x ^{3} ( x + 2 ) ^{3}} d x

\frac{3}{16} ln ∣ x ∣ + \frac{3}{16 x} - \frac{1}{16 x ^{2}} - \frac{3}{16} ln ∣ x + 2 ∣ + \frac{3}{16 ( x + 2 )} + \frac{1}{16 ( x + 2 ) ^{2}} + C

求解步骤

\int \frac{1}{x ^{3} ( x + 2 ) ^{3}} d x

将

\frac{1}{x ^{3} ( x + 2 ) ^{3}}

用部份分式展开:

\frac{3}{16 x} - \frac{3}{16 x ^{2}} + \frac{1}{8 x ^{3}} - \frac{3}{16 ( x + 2 )} - \frac{3}{16 ( x + 2 ) ^{2}} - \frac{1}{8 ( x + 2 ) ^{3}}

= \int \frac{3}{16 x} - \frac{3}{16 x ^{2}} + \frac{1}{8 x ^{3}} - \frac{3}{16 ( x + 2 )} - \frac{3}{16 ( x + 2 ) ^{2}} - \frac{1}{8 ( x + 2 ) ^{3}} d x

使用积分加法定则:

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

= \int \frac{3}{16 x} d x - \int \frac{3}{16 x ^{2}} d x + \int \frac{1}{8 x ^{3}} d x - \int \frac{3}{16 ( x + 2 )} d x - \int \frac{3}{16 ( x + 2 ) ^{2}} d x - \int \frac{1}{8 ( x + 2 ) ^{3}} d x

\int \frac{3}{16 x} d x = \frac{3}{16} ln ∣ x ∣

\int \frac{3}{16 x ^{2}} d x = - \frac{3}{16 x}

\int \frac{1}{8 x ^{3}} d x = - \frac{1}{16 x ^{2}}

\int \frac{3}{16 ( x + 2 )} d x = \frac{3}{16} ln ∣ x + 2 ∣

\int \frac{3}{16 ( x + 2 ) ^{2}} d x = - \frac{3}{16 ( x + 2 )}

\int \frac{1}{8 ( x + 2 ) ^{3}} d x = - \frac{1}{16 ( x + 2 ) ^{2}}

= \frac{3}{16} ln ∣ x ∣ - (- \frac{3}{16 x}) - \frac{1}{16 x ^{2}} - \frac{3}{16} ln ∣ x + 2 ∣ - (- \frac{3}{16 ( x + 2 )}) - (- \frac{1}{16 ( x + 2 ) ^{2}})

化简

= \frac{3}{16} ln ∣ x ∣ + \frac{3}{16 x} - \frac{1}{16 x ^{2}} - \frac{3}{16} ln ∣ x + 2 ∣ + \frac{3}{16 ( x + 2 )} + \frac{1}{16 ( x + 2 ) ^{2}}

解答补常数

= \frac{3}{16} ln ∣ x ∣ + \frac{3}{16 x} - \frac{1}{16 x ^{2}} - \frac{3}{16} ln ∣ x + 2 ∣ + \frac{3}{16 ( x + 2 )} + \frac{1}{16 ( x + 2 ) ^{2}} + C

\int (2 - x) (1 + x) (1 - x)^{\frac{3}{2}} d x

\int \frac{( 3 x + 2 ) ( x - 4 )}{x - 3} d x

\int x^{2} + 8 x^{5} d x

\int \frac{x}{- 9 x ^{2} + 24 x + 20} d x

\int 7 x csc (x^{2}) d x