`(x^2-x+3)(x^2-x-2) + 4`
Đặt `x^2 - x + 0,5 = a`
`=> ``(x^2-x+3)(x^2-x-2) + 4`
` = (a+2,5)(a - 2,5) + 4`
` = a^2 - 6,25 + 4`
` = a^2 - 2,25`
`= a^2 - 1,5^2`
` = (a-1,5)(a+1,5)`
` = (x^2-x+0,5 - 1,5)(x^2 - x + 0,5 + 1,5)`
` = (x^2 - x - 1)(x^2 - x + 2)`