Question

Usando o método de completar quadrado,

determine as raízes das equações do segundo grau e

assinale a alternativa correta:

1) x² + 12x + 32 = 0

(A) S={-8, -4} (C) S={0, 1}

(B) S={-4, 4} (D) S={-8, 8}

2) x² + 6x – 7 = 0

(A) S={0, -5} (C) S={1, 7}

(B) S={-10, 10} (D) S={-7, 1}

3) x

2 + 6x + 8 = 0

(A) S={-3, 5} (C) S={0, 6}

(B) S={-4, -2} (D) S={-4, 4}

4) x

2 + 2x – 8 = 0

(A) S={-4, -2} (C) S={0, 2}

(B) S={-2, 2} (D) S={-4, 2}
​

Answer 1

Explicação passo-a-passo:

1)

x² + 12x + 32 = 0

x² + 4x + 8x + 32 = 0

x.(x + 4) + 8.(x + 4) = 0

(x + 4).(x + 8) = 0

• x + 4 = 0

x' = -4

• x + 8 = 0

x" = -8

S = {-8, -4}

Letra A

2)

x² + 6x - 7 = 0

x² - x + 7x - 7 = 0

x.(x - 1) + 7.(x - 1) = 0

(x - 1).(x + 7) = 0

• x - 1 = 0

x' = 1

• x + 7 = 0

x" = -7

S = {-7, 1}

Letra D

3)

x² + 6x + 8 = 0

x² + 2x + 4x + 8 = 0

x.(x + 2) + 4.(x + 2) = 0

(x + 2).(x + 4) = 0

• x + 2 = 0

x' = -2

• x + 4 = 0

x" = -4

S = {-4, -2}

Letra B

4)

x² + 2x - 8 = 0

x² - 2x + 4x - 8 = 0

x.(x - 2) + 4.(x - 2) = 0

(x - 2).(x + 4) = 0

• x - 2 = 0

x' = 2

• x + 4 = 0

x" = -4

S = {-4, 2}

Letra D