（1）ab分之a(chǎn)-b+bc分之b-c+ca分之c-a
=(ac-bc+ab-ac+bc-ab)/abc
=0/abc
=0
（2）x-1分之1-x+1分之1-x^2+1分之2
=(x+1-x+1)/(x²-1)-2/(x²+1)
=2/(x²-1)-2/(x²+1)
=(2x²-2-2x²-2)/(x^4-1)
=-4/(x^4-1)
（3）x-y + x+y分之2y^2
=(x²-y²+2y²)/(x+y)
=(x²+y²)/(x+y)
（4）x+2y+ x-2y分之4y^2+ 4y^2-x^2分之4x²y
=(x²-4y²+4y²)/(x-2y)-4x²y/(x²-4y²)
=(x²+2x²y-4x²y)/(x²-4y²)
=(x²-2x²y)/(x²-4y²)
（5）（1+ x-1分之1）÷ x^2-1分之x^2
=(x-1+1)/(x-1)÷x²/(x-1)(x+1)
=x/(x-1)*(x+1)(x-1)/x²
=(x+1)/x