$a=3$a=3 i $b=4$b=4

$\displaystyle a=- \frac{1}{3}$\displaystyle a=- \frac{1}{3} i $b=4$b=4

$a=3$a=3 i $b=-4$b=-4

$\displaystyle a=- \frac{1}{3}$\displaystyle a=- \frac{1}{3} i $b=6$b=6