Resposta :
1. 2x² + 8x = 0
x . (2x + 8) = 0
x' = 0
2x + 8 = 0
2x = -8
x = -8/2
x = -4
x" = -4
Letra C.
2. (x + 3) . (x + 1) = 2
x² + x + 3x + 3 = 2
x² + 4x + 3 - 2 = 0
x² + 4x + 1 = 0
Letra A.
3. x² + 8x = 0
x . (x + 8) = 0
x' = 0
x + 8 = 0
x = -8
x" = -8
Letra C.
4. x² - 7x - 2c = 0
(-3)² - 7 . (-3) - 2c = 0
9 - (-21) - 2c = 0
9 + 21 - 2c = 0
30 - 2c = 0
-2c = -30
c = -30/-2
c = 15
Letra B.
5. x² - 2x - 8 = 0
a = 1
b = -2
c = -8
Δ = b² - 4 . a . c
Δ = (-2)² - 4 . 1 . (-8)
Δ = 4 - 4 . (-8)
Δ = 4 - (-32)
Δ = 4 + 32
Δ = 36
x = -b ± √Δ /2 . a
x = -(-2) ± √36 /2 . 1
x = 2 ± 6 /2
x' = 2 - 6 /2
x' = -4/2
x' = -2
x" = 2 + 6 /2
x" = 8/2
x" = 4
Letra C