integral of ((x^7+1))/(sqrt(x^8+8x))

解答

\int \frac{( x ^{7} + 1 )}{x ^{8} + 8 x} d x

\frac{1}{4} x^{8} + 8 x + C

求解步骤

\int \frac{x ^{7} + 1}{x ^{8} + 8 x} d x

使用换元积分法

= \int \frac{1}{8 u} d u

提出常数:

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

= \frac{1}{8} \cdot \int \frac{1}{u} d u

使用幂法则

= \frac{1}{8} \cdot 2 u^{\frac{1}{2}}

u = x^{8} + 8 x

代回

= \frac{1}{8} \cdot 2 (x^{8} + 8 x)^{\frac{1}{2}}

化简

\frac{1}{8} \cdot 2 (x^{8} + 8 x)^{\frac{1}{2}} : \frac{1}{4} x^{8} + 8 x

= \frac{1}{4} x^{8} + 8 x

解答补常数

= \frac{1}{4} x^{8} + 8 x + C

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