下面这道的简便运算。
(1+1/2)×(1-1/2)×(1+1/3)×(1-1/3)×…×(1+1/99)×(1-1/99)
=(1-1/2)(1+1/2)(1-1/3)(1+1/3)(1-1/4)(1+1/4)……(1-1/99)(1+1/99)
=1/2 ×3/2×2/3 × 4/3×3/4 × ……×98/99 ×100/99
=1/2×100/99
=50/99
分成两个式子,+号的和-号的分开来
(1+1/2)×(1+1/3)×(1+1/4)×……×(1+1/100)
=3/2×4/3×5/4×6/5×……×100/99+101/100
=101/2(前一个分子和后一个分母相消了)
减号的式*子同理
=1/2×2/3×3/4×……×98/99*99/100
=1/100(前一个分母和后一个分子相消了)
101/2×1/100=101/200
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