Question

x ( x + 3)= 5x + 15 ​

Answer 1

x (x + 3) = 5x + 15

x² + 3x = 5x + 15

x² + 3x - 5x - 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)}