sum from n=1 to infinity of (3n)x^n

解答

n = 1 \sum \infty (3 n) x^{n}

收敛半径为 1, 收敛区间为 - 1 < x < 1

求解步骤

n = 1 \sum \infty 3 n x^{n}

使用比值审敛法计算收敛区间

收敛半径为 1, 收敛区间为 - 1 < x < 1

\frac{\partial}{\partial x} (9 x y^{2})

\int_{0}^{2} (1 - 2 x) d x

\int \frac{2 x ^{3} + x ^{2} + 8 x - 12}{x ^{3} + 4 x} d x

s l o p e (0) (1.2)

l a pl a ce t r an s f or m 35 t^{2}