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受欢迎的微积分 >

integral of (2x+1)/(x^2+2x+65)

解答

\int \frac{2 x + 1}{x ^{2} + 2 x + 65} d x

解答

ln x^{2} + 2 x + 65 - \frac{1}{8} arctan (\frac{1}{8} (x + 1)) + C

求解步骤

\int \frac{2 x + 1}{x ^{2} + 2 x + 65} d x

对

x^{2} + 2 x + 65

配方:

(x + 1)^{2} + 64

= \int \frac{2 x + 1}{( x + 1 ) ^{2} + 64} d x

使用换元积分法

= \int \frac{2 u - 1}{u ^{2} + 64} d u

乘开

\frac{2 u - 1}{u ^{2} + 64} : \frac{2 u}{u ^{2} + 64} - \frac{1}{u ^{2} + 64}

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{2 u}{u ^{2} + 64} d u - \int \frac{1}{u ^{2} + 64} d u

\int \frac{2 u}{u ^{2} + 64} d u = ln u^{2} + 64

\int \frac{1}{u ^{2} + 64} d u = \frac{1}{8} arctan (\frac{u}{8})

= ln u^{2} + 64 - \frac{1}{8} arctan (\frac{u}{8})

u = x + 1

代回

= ln (x + 1)^{2} + 64 - \frac{1}{8} arctan (\frac{x + 1}{8})

化简

ln (x + 1)^{2} + 64 - \frac{1}{8} arctan (\frac{x + 1}{8}) : ln x^{2} + 2 x + 65 - \frac{1}{8} arctan (\frac{1}{8} (x + 1))

= ln x^{2} + 2 x + 65 - \frac{1}{8} arctan (\frac{1}{8} (x + 1))

解答补常数

= ln x^{2} + 2 x + 65 - \frac{1}{8} arctan (\frac{1}{8} (x + 1)) + C

作图

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