-2(2xy+2x)+3(-2xy-5x)
=-4xy-4x-6xy-15x
=-10xy-19x
(-1/3+m的2次方n+m的平方)-(2/3-m的平方n-m的立方)
=-1/3+m²n+m²-2/3+m²n+m²
=2m²n+2m²-1