`a)(2x+3)(2x²-y+1)`
`=2x.2x²-2x.y+2x.1+3.2x²-3.y+3.1`
`=4x³-2xy+2x+6x²-3y+3`
`b)(3x²-5x+z)(5x-1)`
`=3x².5x-3x².1-5x.5x+5x.1+z.5x-z.1`
`=15x³-3x²-25x²+5x-5xz-z`
`=15x³-(3x²+25x²)+5x-5xz-z`
`=15x³-28x²+5x-5xz-z`
`c)(4x-1)(3x²+2x+1)`
`=4x.3x²+4x.2x+4x.1-1.3x²-1.2x-1.1`
`=12x³+8x²+4x-3x²-2x-1`
`=12x³+(8x²-3x²)+(4x-2x)-1`
`=12x³+5x²+2x-1`
`d)2x(2x^4-4xy+1)`
`=2x.2x^4-2x.4xy+2x.1`
`=4x^5-8x²y+2x`
`e)(4xy-2y+1).4x³`
`=4xy.4x³-2y.4x³+1.4x³`
`=16x^4y-8x³y+4x³`
