`M = -7x(x-5) -(x-1)(x^2-x-2) + x^2(x-3) - 5x(x-8)`
`-> M = -7x^2 +35 -x^3 + x^2 +2x - x^2 + x + 2 + x^3 + 3x^2 -5x^2 -8`
`-> M = (-7x^2+x^2 -x^2+3x^2-5x^2) + (35 - 8 +2) +(-x^3+x^3) + (2x+x) `
`-> M = -9x^2+29 +3x`
Thay `x =1/2` vào `M`
`-> M = -9 . (1/2)^2 +29 + 3/2`
`-> M = -9/4 +29 +3/2`
`-> M = 28,25`