Question

resolva as seguintes questões do 2° grau: a) x² - 4× - 5 =0 b) ײ + 8× + 20 =0 C) 9ײ +6 +1 =0​

Answer 1

a) x² - 4x - 5 = 0

a = 1

b = - 4

c = - 5

∆ = b² - 4 . a . c

∆ = (-4)² - 4 . 1 . (-5)

∆ = 16 + 20

∆ = 36

x = - b ± √∆

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2a

x' = -(-4) - 6

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2 . 1

x' = 4 - 6

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2

x' = - 2

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2

x' = - 1

x" = -(-4) + 6

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2 . 1

x" = 4 + 6

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2

x" = 10

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2

x" = 5

S = {-1, 5}

b) x² + 8x + 20 = 0

a = 1

b = 8

c = 20

∆ = b² - 4 . a . c

∆ = 8² - 4 . 1 . 20

∆ = 64 - 80

∆ = - 16

delta negativo não há raízes reais

S = { }

c) 9x² + 6x + 1 = 0

a = 9

b = 6

c = 1

∆ = b² - 4 . a . c

∆ = 6² - 4 . 9 . 1

∆ = 36 - 36

∆ = 0

x = - b ± √∆

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2a

x = - 6 - 0

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2 . 9

x = - 6 (÷6)

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18 (÷6)

x = - 1

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3

S = {-1/3}