Answer
$(-3+4i)^2+6(-3+4i)+25=0$
Work Step by Step
In order to see that $-3+4i$ is a solution, we plug it in and make sure the equation remains true.
$(-3+4i)^2+6(-3+4i)+25=0?$
Expand the left hand side.
$9-24i+16i^2-18+24i+25$
Combine like terms using the fact that $i^2=-1$.
$(9-16-18+25)+(-24+24)i=0$
$(-3+4i)^2+6(-3+4i)+25=0$
