Question

equação irracional x - 1 = raiz quadrada de 3 x mais 15???

Answer 1

$x-1=\sqrt{3x+15}\\\\(x-1)^2=(\sqrt{3x+15})^2\\\\x^2-2x+1=3x+15\\\\x^2-5x-14=0\\\\x=-2\ ou\ x=7$

Porem temos que testar os resultados.

$x-1=\sqrt{3x+15}\\\\(-2)-1=\sqrt{3(-2)+15}\\\\-3=\sqrt{9}\\\\-3=3\ \ (falso)\\\\(7)-1=\sqrt{3(7)+15}\\\\6=\sqrt{36}\\\\6=6\ \ (verdadeiro)$

Portanto a unica resposta valida eh x=7