sum from n=0 to infinity}((-4)^{3n of)/(5^{n-1)}

解答

n = 0 \sum \infty \frac{( - 4 ) ^{3 n}}{5 ^{n - 1}}

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求解步骤

n = 0 \sum \infty \frac{( - 4 ) ^{3 n}}{5 ^{n - 1}}

使用级数比值审敛法:

发散

= 发散

\int [\frac{1}{( 4 + x ^{2} )}] d x

x \to - 5 lim (\frac{x + 4}{x + 5})

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

t a y l or \frac{1}{( 1 - x )}, 0

l a pl a ce t r an s f or m x