1..(2x-3y)/(y-x)-(x+2y)/(x-y)
=（2x-3y+x+2y）/(y-x)
=(3x-y)/(y-x)
2.5m/(m-3)+2m/(m+3)]*(m^2-9)/m
=[5m(m+3)+2m(m-3)]/(m^2-9)*(m^2-9)/m
=(7m²+9m)/m
=7m+9