# Graphing an exponential function

I think you're graphing $y = (-2)^x$ instead of $y = -2^x$. There is a big difference.
$(-2)^4 = 16$ but $-2^2 = -2 \cdot 2 \cdot 2 \cdot 2 = -(2^4) = -16$
For the former graph, you will get a bunch of scattered points that don't form a smooth curve. However, the latter graph produces $y = 2^x$ but reflected over the x-axis.