$$\left. \begin{array} { l } { 3 x ^ { 2 } - 7 x - c = 0 } \\ { c = ? } \end{array} \right.$$
$x=\frac{\sqrt{12c+49}+7}{6}$
$x=\frac{-\sqrt{12c+49}+7}{6}\text{, }c=d$
$x=\frac{\sqrt{12c+49}+7}{6}$
$x=\frac{-\sqrt{12c+49}+7}{6}\text{, }c\geq -\frac{49}{12}\text{ and }d=c$
