(x-1分之1-x+1分之1)除以2x平方-2分之x
=[1/(x-1)-1/(x+1)]÷x/2(x²-1)
=(x+1-x+1)/(x²-1)÷x/2(x²-1)
=2*2/x
=4/x x=1
=4/1
=4