ab+a-mb-m
=b(a-m)+(a-m)
=(b+1)(a-m)
(1-2的平方分之1)(1-3的平方分之1)(1-4的平方分之1)……(1-9的平方分之1)(1-10的平方分之1)
=(1-1/2)(1+1/2)(1-1/3)(1+1/3)(1-1/4)(1+1/4).(1-1/9)(1+1/9)
=(1/2)×(3/2)×(2/3)(4/3)(3/4)(5/4).(8/9)(10/9)
=(1/2)×(10/9)
=5/9
ab+a-mb-m
=b(a-m)+(a-m)
=(b+1)(a-m)
(1-2的平方分之1)(1-3的平方分之1)(1-4的平方分之1)……(1-9的平方分之1)(1-10的平方分之1)
=(1-1/2)(1+1/2)(1-1/3)(1+1/3)(1-1/4)(1+1/4).(1-1/9)(1+1/9)
=(1/2)×(3/2)×(2/3)(4/3)(3/4)(5/4).(8/9)(10/9)
=(1/2)×(10/9)
=5/9