Bonjour
a^2 - b^2 = (a - b)(a + b)
Factoriser 16 x au carré moins 81 (4x_7)au carré moins 9x au carré
16x^2 - 81
= (4x)^2 - 9^2
= (4x - 9)(4x + 9)
(4x - 7)^2 - 9x^2
= (4x - 7)^2 - (3x)^2
= (4x - 7 - 3x)(4x - 7 + 3x)
= (x - 7)(7x - 7)
= (x - 7) * 7(x - 1)
= 7(x - 7)(x - 1)
