$a=-4$a=-4 i $b=-2$b=-2

$\displaystyle a= \frac{1}{4}$\displaystyle a= \frac{1}{4} i $\displaystyle b= -\frac{1}{8}$\displaystyle b= -\frac{1}{8}

$a=-4$a=-4 i $b=2$b=2

$\displaystyle a= \frac{1}{4}$\displaystyle a= \frac{1}{4} i $\displaystyle b= \frac{1}{2}$\displaystyle b= \frac{1}{2}