`\qquad-4x^5(x^3-4x^2+7x-3)`
`=-4x^5.x^3+(-4x^5).(-4x^2)+(-4x^5).7x+(-4x^5).(-3)`
`=-4x^8+16x^7-28x^6+12x^5`
-----------------------------------
`\qquad3/5 x^2y(-5/3xy-10x+5y)`
`=3/5x^2y. (-5/3xy)+3/5x^2y.(-10x)+3/5x^2y.5y`
`=-x^3y^2-6x^3y+3x^2y^2`
-----------------------------------
`\qquad5x^2-3x(x+2)`
`=5x^2-3x^2-6x`
`=2x^2-6x`
-----------------------------------
`-4x(3x-4)+7x(x-5)`
`=-12x^2+16x+7x^2-35x`
`=-5x^2-19x`
