Bonsoir,
A = (√x - √y)²
➡️ identité remarquable : (a - b)² = a² - 2ab + b²
A = (√x)² -2(√x × √y) + (√y)²
A = x - 2 × √(xy) + y
A = -2 × √4 + x + y
A = -2 × 2 + 7 = -4 + 7
A = 3 ✅
B = 2x(1 - y) + 2y(1 - 2x)
B = 2x - 2xy + 2y - 4xy
B = 2x + 2y - 6xy
B = 2(x + y) - 6 × 4
B = 2 × 7 - 24 = 14 - 24
B = -10 ✅
C = (x - y)² - (x + y)²
➡️ a² - b² = (a - b)(a + b)
C = (x - y - x - y)(x - y + x + y)
C = -2y × 2x = -4xy
C = -4 × 4 = -16 ✅
Bonne soirée !
