8x-x²(5x-1)
= - 5x^3 + x² + 8x
= -5x(x² - x/5 - 8/5)
x² - x/5 - 8/5
(x - 1/10)² = x² - x/5 + 1/100
donc x² - x/5 - 8/5 =
(x - 1/10)² - 161/100
= (x - 1/10 - (V161)/10)(x - 1/10 + (V161)/10)
= (x - (1+V161)/10)(x - (1- V161)/10)
8x-x²(5x-1)
= -5x(x-(1+V161)/10)(x-(1-V161)/10)
(3x-2)²-(2x-1)(3x-2)
= (3x-2)(3x-2-2x+1)
= (3x-2)(x-1)
En espérant t'avoir aidé.
