分式与
的最简公分母是____________.
计算:
(1)+
=____________
(2)()2=_____________
(3)+
=_______________
(4)-
=____________
(5)1÷(+
)=_________________
约分:(1)=_________________(2)
=________________
当x=1,y=-4时,分式的值是____________.
当x=__________时,分式有意义.
因式分【解析】
(1)9-4a2=________________
(2)-15x3y2+10x2y4-20x4y3=__________________
(3)a2-5ab+6b2=__________________
(4)-m2+4mn-4n2=________________________