[tex]\displaystyle\bf\\3x^{2} +5x+c=0\\\\x_{1} =-2\\\\3\cdot(-2)^{2} +5\cdot(-2)+c=0\\\\3\cdot 4-10+c=0\\\\2+c=0\\\\\boxed{c=-2}\\\\Teorema \ Vieta \ :\\\\x_{1} +x_{2} =-\frac{5}{3} \\\\x_{2} =-\frac{5}{3} -x_{1} =-1\frac{2}{3} -(-2)=-1\frac{2}{3} +2=\frac{1}{3} \\\\\boxed{x_{2} =\frac{1}{3} }[/tex]