Can anyone help me in sketching a graph of N against t from this?

$\displaystyle N(t) = \frac {-6}{25}$t^{2}+ $\displaystyle \frac {6}{5}t$

Maybe then i can figure out how to then sketch a graph of this(Thinking):

$\displaystyle N(t) = \frac {-1}{25}$t$\displaystyle (t – 5) (t + 4)$

If anyone can help i'd be really grateful, thankyou