Question

Rezolvati in multimea numerelor reale ecuatia:
$\sqrt{ 5 - x} = 3x - 1$
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Answer 1

√5 - x = 3x - 1

5 - x = (3x - 1)²

5 - x = 9x² - 6x + 1

9x² - 5x - 4 = 0

Δ = b² - 4ac

Δ = 25 - 4(-4×9) = 25 + 144 = 169

x₁ = (- b - √Δ)/2a = (5 - 13)/18 = - 8/18 = - 4/9

x₂ = (- b + √Δ)/2a = (5 + 13)/18 = 18/18 = 1