a)
E = (3x + 2)² - (3x + 2) (x + 7)
= (3x + 2) (3x +2) - (3x + 2) (x + 7)
= (3x * 3x + 3x * 2 + 2 * 3x + 2 * 2) - (3x * x + 3x * 7 + 2 * x + 2 * 7)
= (9x² + 6x + 6x + 4) - (3x² + 21x + 2x + 14)
= 9x² + 12x + 4 - 3x² - 21x - 2x - 14
= 6x² - 11x - 10.
b)
E = (3x + 2)²- (3x + 2) (x + 7)
= (3x + 2) (3x + 2) - (3x + 2) (x + 7)
= (3x + 2) [(3x + 2) - (x+7)]
= (3x + 2) (3x + 2 -x -7)
= (3x + 2) (2x -5)
c) Si x = 1
2
E= 6 x 1 - 11 x 1 - 10
2 2
= 6 - 11 - 10
2 2
= 5 - 10
2
= 5 - 10
2 1
= 5 - 20
2 2
= -15
2
= -7,5.
Voilàà.
