Question

(x + 3) . ( x - 5) =
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Answer 1

(x + 3) . (x - 5)

x² - 5x + 3x - 15

x² - 2x - 15 = 0

a = 1

b = - 2

c = - 15

∆ = b² - 4 . a . c

∆ = (-2)² - 4 . 1 . (-15)

∆ = 4 + 60

∆ = 64

x = - b ± √∆

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2a

x' = - (-2) - 8

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2 . 1

x' = 2 - 8

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2

x' = - 6

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2

x' = - 3

x" = - (-2) + 8

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2 . 1

x" = 2 + 8

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2

x" = 10

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2

x" = 5

S = {-3 , 5}