$r=-16$r=-16

$\displaystyle r=- \frac{1}{2}$\displaystyle r=- \frac{1}{2}

$\displaystyle r=- \frac{1}{32}$\displaystyle r=- \frac{1}{32}

$\displaystyle r=15 \frac{1}{2}$\displaystyle r=15 \frac{1}{2}