Question

f(x1-x2)=f(x1)-x2(2x-x1+1)

f(x1)-f(x2)=(2x1-1/x1)-(2x2-1/x2)要怎么化简成（x1-x2)(2+1/x1x2)

Answer 1

f(x1)-f(x2)=(2x1-1/x1)-(2x2-1/x2)
=2x1-2x2+1/x2-1/x1
=2(x1-x2)+x1/x1x2-x2/x1x2
=2(x1-x2)+(x1-x2)(1/x1x2)
=(x1-x2)(2+1/x1x2)