Answer
$\color{blue}{\left\{-\dfrac{\sqrt{70}}{5}, \dfrac{\sqrt{70}}{5}\right\}}$
Work Step by Step
Add $14$ to both sides to obtain:
\begin{align*}
5t^2&=14\\
t^2&=\frac{14}{5}
\end{align*}
Take the square root of both sides to obtain:
\begin{align*}
\sqrt{t^2}&=\pm\sqrt{\frac{14}{5}}\\\\
t&=\pm\sqrt{\frac{14}{5}}\\\\
t&=\pm\sqrt{\frac{14\cdot 5}{5\cdot 5}}\\\\
t&=\pm\sqrt{\frac{70}{5^2}}\\\\
t&=\pm \frac{\sqrt{70}}{5}\\\\
\end{align*}
Therefore, the solution set is $\color{blue}{\left\{-\dfrac{\sqrt{70}}{5}, \dfrac{\sqrt{70}}{5}\right\}}$.
