Question

O triplo do quadrado de x , somado ao dobro de x , é igual a -5 . Qual é o valor de X ?

Answer 1

$3* x^{2} +2x=5\to \\\\3 x^{2} +2x-5=0\\\\ a=3;b=2;c=5\\\\\\ \Delta=b^2-4ac\to \Delta=2^2-4*3*(-5)\to \Delta=4+60\to \Delta=64\\\\\\ x= \frac{-b+- \sqrt{\Delta} }{2a} \to x= \frac{-2+- \sqrt{64} }{2*3} \to x= \frac{-2+-8 }{6} \to \\\\\\ x'= \frac{-2+8 }{6} \to x'= \frac{6 }{6} \to x'=1\\\\\\ x''= \frac{-2-8 }{6} \to x''= \frac{-10 }{6} \to x= \frac{-5 }{3} \\\\\\ S=(\frac{-5 }{3};1)$




$Verificando:\\\\ Para\to x=1\\\\ 3* x^{2} +2x=5\to 3* 1^{2} +2*1=5\to 3+2=5\to 5=5\\\\Verdadeira\\\\ \\\\Para\to x= \frac{-5}{3} \\\\3* x^{2} +2x=5\to 3*( \frac{-5}{3})^{2} +2*(\frac{-5}{3})=5\to \\ 3*( \frac{25}{9}) +(\frac{-10}{3})=5\to ( \frac{75}{9}) -(\frac{10}{3})=5\to mmc=9\\ 75-30=35\to 45=35\\\\Falsa$