Question

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Urgente
x^2-3(x+1)=15

Answer 1

x² - 3(x + 1) = 15

x² - 3x - 3 = 15

x² - 3x - 18 = 0

Resolvendo a equação do 2º grau

$x= \frac{-b+- \sqrt{ b^{2} 4.a.c} }{2.a}$

$x= \frac{3+- \sqrt{ 3^{2} -4.1.(-18)} }{2.1}$

$x= \frac{3+- \sqrt{9+72} }{2}$

$x= \frac{3+- \sqrt{81} }{2}$

$x'= \frac{3+9}{2}$

$x'= \frac{12}{2}$

x' = 6

$x''= \frac{3-9}{2}$

$x''= \frac{-6}{2}$

x''= -3