bonjour
1)
D(x) = (x - 2)² - 2(x - 2)
= x² - 2*x*2 + 2² - 2x - 2*(-2)
= x² - 4x + 4 -2x + 4
= x² - 4x - 2x + 4 + 4
= x² - 6x + 8
= x² - 6x + 8
2)
calculer D(1)
on remplace x par 1
D(1) = 1² - 6*1 + 8
= 1 - 6 + 8
= 9 - 6
= 3
3) factoriser
(x - 2)² - 2(x - 2) = (x - 2)(x - 2) - 2(x - 2) [facteur commun : x - 2]
= (x - 2)(x - 2) - 2(x - 2) (on le met en facteur)
= (x - 2)(x - 2) - 2)
= (x - 2)(x - 4)
