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受欢迎的微积分 >

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

解答

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

解答

\frac{1}{2} ln 2 x^{2} + 22 x + 2 + arctan (2 x + 1) + C

求解步骤

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

对

x^{2} + 2 x + 1

配方:

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

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

使用换元积分法

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

提出常数:

\int a \cdot f (x) d x = a \cdot \int f (x) d x

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

乘开

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

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

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

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

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

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

u = x + \frac{1}{2}

代回

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

化简

2 (\frac{1}{2 2} ln 2 (x + \frac{1}{2})^{2} + 1 + \frac{1}{2} arctan (2 (x + \frac{1}{2}))) : \frac{1}{2} ln 2 x^{2} + 22 x + 2 + arctan (2 x + 1)

= \frac{1}{2} ln 2 x^{2} + 22 x + 2 + arctan (2 x + 1)

解答补常数

= \frac{1}{2} ln 2 x^{2} + 22 x + 2 + arctan (2 x + 1) + C

作图

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