Answer
$z=7.5$ or $z=-9$
Work Step by Step
$2z^2+3z=135$
$z^2+\frac{3}{2}z=\frac{135}{2}$
$z^2+2.m.\frac{3}{4}+\frac{9}{16} =\frac{135}{2}+\frac{9}{16}$
$(z+\frac{3}{4})^2=(\frac{1089}{16})$
$(z+\frac{3}{4})^2=(\frac{33}{4})^2$
$z+\frac{3}{4}=\pm \frac{33}{4}$
$z+\frac{3}{4}=\frac{33}{4}$ or $z+\frac{3}{4}=-\frac{33}{4}$
$z=7.5$ or $z=-9$
