Bonjour
A = 4(5y + 6) -4y(5y + 6) + y²(5y + 6)
1) si y = 2, alors A = 4(5*2 + 6) -4*2(5*2 + 6) + 2²(5*2 + 6)
A = 4(10 + 6) - 8(10 + 6) + 4(10 + 6)
A = 4*16 - 8*16 + 4*16
A = 0
2) A = 4(5y + 6) -4y(5y + 6) + y²(5y + 6)
A = (5y + 6)(4 - 4y + y²)
A = (5y + 6)(y - 2)²
3) 4(5y + 6) -4y(5y + 6) + y²(5y + 6) = 0
(5y + 6)(y - 2)² = 0
5y + 6 = 0 ou (y - 2)² = 0
5y = -6 ou y - 2 = 0
y = -6/5 ou y = 2
S = {-6/5 ; 2}