快(1+1/2)乘（1-1/2)乘(1+1/3)乘(1-1/3)乘.乘(1+1/99)乘(1-1/99)(1-1/2乘1

(1+1/2)乘（1-1/2)乘(1+1/3)乘(1-1/3)乘.乘(1+1/99)乘(1-1/99)
=3/2*4/3*5/4*...*100/99*1/2*2/3*3/4*...*98/99
=100/2*1/99
=50/99
(1-1/2乘1/2)乘(1-1/3乘1/3)乘(1-1/4乘1/4)乘.乘(1-1/2005乘1/2005)
=(1+1/2)(1-1/2)...(1+1/2005)(1-1/2005)
=3/2*4/3*...*2006/2005*1/2*2/3*...*2004/2005
=2006/2*1/2005
=1003/2005
4.75乘1.36除以4.75除以0.68除以0.375乘0.75
=4.75*1.36/4.75/0.68/0.375*0.75
=4.75/4.75*1.36/0.68*0.75/0.375
=1*2*2
=4