Question

como resolver essa equação : log3 (2x+7)+ log3(x-1)=5

Answer 1

$log\ _3\ (2x+7)+log\ _3\ (x-1) = 5\\\\ log\ _3\ (2x+7)*(x-1)=5\\\\\ 3^5 = (2x+7)*(x-1)\\\\\ 243 = 2x^2-2x+7x-7\\\\\\ 2x^2+5x+250 = 0\\\\ \Delta = 25+2000\\\\ \Delta= 2025\\\\\ x^i = 20\\\\ x^i^i = -25\\\\\ \boxed{\therefore\ x=20}$