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受欢迎的微积分 >

integral of x/(sqrt(-7-8x-x^2))

解答

\int \frac{x}{- 7 - 8 x - x ^{2}} d x

解答

- - x^{2} - 8 x - 7 - 4 arcsin (\frac{1}{3} (x + 4)) + C

求解步骤

\int \frac{x}{- 7 - 8 x - x ^{2}} d x

对

- 7 - 8 x - x^{2}

配方:

- (x + 4)^{2} + 9

= \int \frac{x}{- ( x + 4 ) ^{2} + 9} d x

使用换元积分法

= \int \frac{u - 4}{- u ^{2} + 9} d u

乘开

\frac{u - 4}{- u ^{2} + 9} : \frac{u}{- u ^{2} + 9} - \frac{4}{- u ^{2} + 9}

= \int \frac{u}{- u ^{2} + 9} - \frac{4}{- u ^{2} + 9} d u

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{u}{- u ^{2} + 9} d u - \int \frac{4}{- u ^{2} + 9} d u

\int \frac{u}{- u ^{2} + 9} d u = - - u^{2} + 9

\int \frac{4}{- u ^{2} + 9} d u = 4 arcsin (\frac{1}{3} u)

= - - u^{2} + 9 - 4 arcsin (\frac{1}{3} u)

u = x + 4

代回

= - - (x + 4)^{2} + 9 - 4 arcsin (\frac{1}{3} (x + 4))

乘开

- (x + 4)^{2} + 9 : - x^{2} - 8 x - 7

= - - x^{2} - 8 x - 7 - 4 arcsin (\frac{1}{3} (x + 4))

解答补常数

= - - x^{2} - 8 x - 7 - 4 arcsin (\frac{1}{3} (x + 4)) + C

作图

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