分式计算 (10 18:27:49)
1.20a^2b分之5ab=                           
2.x-2分之x^2 - 4x+4=
3.x+y分之x+y + x分之y=
4.x-2分之x-1 + 2-x分之1=
5.ab^2分之(ab)^2=