$b=4$b=4

$\displaystyle b=- \frac{3}{2}$\displaystyle b=- \frac{3}{2}

$\displaystyle b=- \frac{8}{3}$\displaystyle b=- \frac{8}{3}

$\displaystyle b= \frac{4}{3}$\displaystyle b= \frac{4}{3}