Bài làm :
10,
`(-4x+2y)(-4y-2y)+(x-5y)^2-(3x+2y)^2-7x(x-3y)`
`=(-4x).(-4y)+(-4x).(-2y)+2y.(-4y)+2y.(-2y)+[x^2-2.x.5y+(5y)^2]-[(3x)^2-2.3x.2y+(2y)^2]-7x.x-7x.(-3y)`
`=16xy+8xy+(-8y^2)+(-4y^2)+(x^2-10xy+25y^2)-(9x^2-12xy+4y^2)-7x^2-(-21xy)`
`=16xy+8xy-8y^2-4y^2+x^2-10xy+25y^2-9x^2+12xy-4y^2-7x^2+21xy`
`=(16xy+8xy-10xy+12xy+21xy)+(-8y^2-4y^2+25y^2-4y^2)+(x^2-9x^2-7x^2)`
`=47xy+(-9y^2)+(-15x^2)`
`=47xy-9y^2-15x^2`