sum from n=1 to infinity of (2n)/(n^2)

解答

n = 1 \sum \infty \frac{2 n}{n ^{2}}

发散

求解步骤

n = 1 \sum \infty \frac{2 n}{n ^{2}}

使用常数相乘法则:

\sum c \cdot a_{n} = c \cdot \sum a_{n}

= 2 \cdot n = 1 \sum \infty \frac{n}{n ^{2}}

约分:

n

= 2 \cdot n = 1 \sum \infty \frac{1}{n}

使用柯西收敛条件::

发散

= 2 发散

= 发散

d er i v a t i v e y = - 8 x ln (6 x + 5)

t an g e n t y = (x^{3} - 16 x)^{12}, (4, 0)

\frac{d}{d y} (arctan (x + 2 y))

x \to 2 lim (20 - x^{2})

\frac{d}{d x} (x - 2)