(1+2/1)*(1+4/1)*(1+6/1)*...*(1+20/1)*(1-3/1)*(1-5/1)*(1-7/1)*...*(1-21/1)等于多少
问题描述:
(1+2/1)*(1+4/1)*(1+6/1)*...*(1+20/1)*(1-3/1)*(1-5/1)*(1-7/1)*...*(1-21/1)
等于多少
答
(1+1/2)×(1+1/4)×(1+1/6)×……×(1+1/20)×(1-1/3)×(1-1/5)×(1-1/7)×……×(1-1/21)
=3/2×5/4×7/6×……×21/20×2/3×4/5×6/7×……×20/21
=(3/2×2/3)×(5/4×4/5)×(7/6×6/7)×……×(21/20×20/21)
=1×1×1×……×1
=1