Bonjour,
Ces exercices sont des applications de la formule : (a + b)(a - b) = a² - b².
A = (x - 2)(x + 2)
= x² - 2²
= x² - 4.
B = (5 - y)(5 + y)
= 5² - y²
= 25 - y²
C = (3x + 5)(3x - 5)
= (3x)² - 5²
= 9x² - 25
D = (10 - 7z)(10 + 7z)
= 10² - (7z)²
= 100 - 49z²
E = (5 + 4g)(5 - 4g)
= 5² - (4g)²
= 25 - 16g²
F = (2,1x - 3)(2,1x + 3)
= (2,1)² - 3²
= 4,41x² - 9
G = (2i + 6,1)(2i - 6,1)
= (2i)² - 6,1²
= 4i² - 37,21
H = (3,2j + 4)(4 - 3,2j)
= (4 + 3,2j)(4 - 3,2j)
= 4² - (3,2j)²
= 16 - 10,24j²
