Answer
$r= -4.62,r= 3.22$
Work Step by Step
Use the quadratic formula.
$$
r^2+1.4 r-14.9=0.
$$ $$
\begin{aligned}
& a=1 \\
& b=1.4 \\
& c=-14.9
\end{aligned}
$$ $$
\begin{aligned}
r & =\frac{-b \pm \sqrt{b^2-4 a c}}{2 a} \\
& =\frac{-1.4 \pm \sqrt{1.4^2+4 \cdot 14.9}}{2} \\
& =\frac{-1.4 \pm \sqrt{61.56}}{2} \\
& \approx \frac{-1.4 \pm 7.846}{2}.
\end{aligned}
$$ $$
\begin{aligned}
r & =\frac{-1.4-7.846}{2} \\
& =-4.62
\end{aligned}
$$ $$
\begin{aligned}
r & =\frac{-1.4+7.846}{2} \\
& =3.22
\end{aligned}
$$ Define the following function and plot it. We see that the zeros are where they should be.
$$ h(r) = r^2+1.4 r-14.9$$
