$\displaystyle a=- \frac{41}{3}$\displaystyle a=- \frac{41}{3}

$\displaystyle a= \frac{41}{3}$\displaystyle a= \frac{41}{3}

$\displaystyle a=- \frac{47}{3}$\displaystyle a=- \frac{47}{3}

$\displaystyle a= \frac{47}{3}$\displaystyle a= \frac{47}{3}