For the polynomial $-2x^2+14x+16$, the sum of the zeroes and the product of the zeroes are respectively:

Here $a=-2,b=14$ and $c=16$. Sum $=-\frac{b}{a}=-\frac{14}{-2}=7$; product $=\frac{c}{a}=\frac{16}{-2}=-8$. (The zeroes are 8 and −1: they add to 7 and multiply to −8.) The negative leading coefficient is the whole trap: −7 and 8 ignore it, −7 and −8 apply the sign only to the sum, and 14 and 16 simply read off $b$ and $c$ without dividing by a.