bjr
B = (7x - 3)² - x(7x - 3)
il faut penser que (7x - 3)² = (7x - 3)(7x - 3)
B = (7x - 3)(7x - 3) - x(7x - 3) [ le facteur commun est (7x - 3)]
B = (7x - 3)(7x - 3 - x)
B = (7x - 3)(6x - 3) (on met 3 en facteur dans 6x - 3)
B = (7x - 3)*3*(2x - 1)
B = 3(7x - 3)(2x - 1)
C = 2 - x - (2 - x)²
C = (2 - x) - (2 - x)(2 - x)
C = 1*(2 - x) - (2 - x)(2 - x)
C = (2 - x) [ 1 - (2 - x)]
C = (2 - x)(1 - 2 + x)
C = (2 - x)(-1 + x)
= (2 - x)(x - 1)
