Odpowiedź:
f(x) = ( x + 1)² - 9 = x² +2 x + 1 - 9 = x² + 2 x - 8
a = 1 b = 2 c = - 8
Δ = b²- 4 a*c = 2² - 4*1*(-8) = 4 + 32 = 36 √Δ = 6
więc
[tex]x_1 = \frac{-2 - 6}{2*1 } = \frac{- 8}{2} = - 4[/tex] [tex]x_2 = \frac{-2 + 6}{2} = \frac{4}{2} = 2[/tex]
Szczegółowe wyjaśnienie:
[tex]x_1 = \frac{- b - \sqrt{delty} }{2*a}[/tex] [tex]x_2 = \frac{- b + \sqrt{delty} }{2*a}[/tex]
II sposób:
f(x) = ( x + 1)² - 9 = ( x + 1 - 3)*( x + 1 + 3) = ( x - 2)*( x + 4) = 0 ⇔
⇔ x = 2 lub x = - 4
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