Question

Determine as raizes reais das funções a seguir:
a) f(x) = x² - 8x + 15

b) f(x) = x² - 2x - 8

c) f(x) = x² - 6x + 9

Answer 1

Explicação passo-a-passo:

x² - 8x + 15 = 0

a= 1; b = -8; c = 15

D = -8² - 4 . 1 . 15

D = 64 - 60

D = 4

x' = -(-8) + 2

2 .1

x' = 8 + 2

2

x' = 10

2

x' = 5

x" = -(-8) - 2

2 .1

x" = 8 - 2

2

x'' = 6

2

x'' = 3

x² - 2x - 8 = 0

a= 1; b = -2; c = -8

D = -2² - 4 . 1 . (-8)

D = 4 + 32

D = 36

x' = -(-2) + 6

2 .1

x' = 2 + 6

2

x' = 8

2

x' = 4

x" = -(-2) - 6

2 .1

x" = 2 - 6

2

x'' = -4

2

x'' = -2

x² - 6x + 9 = 0

a= 1; b = -6; c = 9

D = -6² - 4 . 1 . 9

D = 36 - 36

D = 0

x' = -(-6) + 0

2 .1

x' = 6 + 0

2

x' = 6

2

x' = 3

x" = -(-6) - 0

2 .1

x" = 6 - 0

2

x'' = 6

2

x'' = 3