`a,(x-8)(x^2-2x+9)+(x+1)^3`
`=x^3-2x^2+9x-(8x^2-16x+72)+(x+1)(x^2+2x+1)`
`=x^3-2x^2+9x-8x^2+16x-72+x^3+2x^2+x+x^2+2x+1`
`=(x^3+x^3)+(-2x^2-8x^2+2x^2+x^2)+(9x+16x+x+2x)+(-72+1)`
`=2x^3-7x^2+28x-71`
`b,(2x-1)^2-3.(x-1).(x+2)-(x+3)^2`
`=4x^2-2*2x+1-3x^2-6x+3x+6-x^2-2x*3-9`
`=4x^2-4x+1-3x^2-6x+3x+6-x^2-6x-9`
`=(4x^2-3x^2-x^2)+(-4x-6x+3x-6x)+(1+6-9)`
`=-13x-2`