计算:(3an+2+6an+1-9an)÷3an-1.
化简:[(3x+2y)(3x-2y)-(x+2y)(5x-2y)]÷4x.
若-a2b÷mab=2a,则m=_______.
计算:(x6y2+x3y5-0.9x2y3)÷(-0.6xy).
计算:18a8b8÷(-6a6b5)·(-ab)2.
下列计算正确的是( )
A.6a2b3÷(3a2b-2ab2)=2b2-3ab B.12a3·(-6a2)÷(-3a)=-4a2+2a
C.(-xy2-3x)÷(-2x)=y2+ D.[(-4x2y)÷2xy2]÷2xy=-2x+y