A = (1 + 7x)² = (1 + 7x)(1 + 7x)
= 1 + 7x + 7x + 49x²
= 1 + 14 x + 49x²
A = 49x² + 14x + 1
B = (4x - 5)² = (4x - 5)(4x - 5)
= 16x² - 20x - 20x + 25
= 16x² - 40x + 25
C = 4x - 6x² = 2x(2 - 3x)
D = 5x² - x = x(5x - 1)
Résoudre ; 6x - 6 = 6 - 2x
6x + 2x = 6 + 6
8x = 12 ⇒ x = 12/8 = 3*4/2*4 = 3/2
6 (3/2) - 6 = 6 - 2(3/2)
18/2 - 6 = 6 - 3
9 - 6 = 6 - 3
3 = 3