Answer
$\left\{\dfrac{-15-\sqrt{785}}{14}, \dfrac{-15+\sqrt{785}}{14}\right\}$
Work Step by Step
The solutions of the quadratic equation $ax^2+bx+c=0$ can be found using the quadratic formula:
$$x=\dfrac{-b\pm\sqrt{b^2-4ac}}{2a}$$
Write the given equation in $ax^2+bx+c=0$ form to obtain:
$$7x^2+15x-20=0$$
The equation above has $a=7, b=15 \text{ and } c= -20$.
Substitute these values into the quadratic formula to obtain:
\begin{align*}
x&=\frac{-15\pm\sqrt{15^2-4(7)(-20)}}{2(7)}\\\\
x&=\frac{-15\pm \sqrt{225+560}}{14}\\\\
x&=\frac{-15\pm \sqrt{785}}{14}\\\\
\end{align*}
Therefore, the solution set is $\color{blue}{\left\{-\dfrac{15-\sqrt{785}}{14}, \dfrac{-15+\sqrt{785}}{14}\right\}}$.
