Hi i need help on where i have gone wrong in the following equations:

1)Solve $\displaystyle (x+2i)(x-2i)=5-12i $ for real values x and y.

$\displaystyle x^2+2ix+2ix+4i^2=5-12i$

$\displaystyle x^2+4ix-4=5-12i$

$\displaystyle x^2+4ix=9-12i$

$\displaystyle 4ix+12i=9-x^2$

$\displaystyle i(4x+12)=9-x^2$

$\displaystyle 4x+12=9-x^2$

$\displaystyle x^2+4x+3$

$\displaystyle (x-1)(x+3)$

x=1 or x=-3

2)Solve $\displaystyle (x+iy)(x+iy)=-18i$ for real values x and y.

$\displaystyle x^2+ixy+ixy+i^2y^2=-18i$

$\displaystyle x^2+2ixy-y^2=-18i$

$\displaystyle 2ixy-18i=x^2-y^2$

$\displaystyle i(2xy-18)=y^2-x^2$

Also another question does $\displaystyle -i^2=1$ and $\displaystyle i^2=-1$

P.S