1/2*1/5即a=1/2,b=1/5
所以1/2*1/5
=(1/2+1/5)÷(1-1/2×1/5)
=7/9
原式=7/9*1/8
=(7/9+1/8)÷(1-7/9×1/8)
=65/65
=1 要分开算