Chapter 6.6, Problem 4E

Let ${\lambda }_1$ and ${\lambda }_2$ be the eigenvalues of
$A=\left(\begin{array}{cc}a& b\\ b& c\end{array}\right)$
What kind of conic section will the equation
$a{x}^2+2bxy+c{y}^2=1$
represent if ${\lambda }_1{\lambda }_2<0?$ Explain.