# Which of the following curves is concave down ?

$\begin{array}{1 1}(1)y=-x^{2}&(2)y=x^{2}\\(3)y=e^{x}&(4)y=x^{2}+2x-3\end{array}$

$y=-x^2$
$x^2=-y$
is a parabola open downward ad is concave downward.
Hence 1 is the correct answer.