題目 Problem 1−13+15−17+19−111+⋯=?1-\dfrac{1}{3}+\dfrac{1}{5}-\dfrac{1}{7}+\dfrac{1}{9}-\dfrac{1}{11}+\cdots=?1−31+51−71+91−111+⋯=? (10%)(10\%)(10%) 解答
