Bonjour !
a)
E = (x-3)² + (x-3)(1-2x)
E = x² - 6x + 9 + x - 2x² - 3 + 6x
E = -x² + x + 6
b)
E = (x-3)² + (x-3)(1-2x)
E = (x-3)(x-3) + (x-3)(1-2x)
E = (x-3)(x - 3 + 1 - 2x)
E = (x-3)(-x -2)
c)
E = (x-3)(-x -2) = 0
Donc soit :
x-3 = 0 : x = 3
Soit :
-x -2 = 0 ; -x = 2 ; x = -2
Voilà !
