a-b分之ab的倒数等于ab分之a-bab分之a-b=a/ab-b/ab=1/b-1/a=-1/2∴a-b分之ab的值等于-2
∵1/a-1/b=1/2 -(a-b)/ab=1/2∴-ab/a-b=2/1 即ab/a-b=-2
