Test Tommorow - Just can't seem to get the hang of it...

1) $\displaystyle y+x^2=4x$

$\displaystyle y+4x=16$

2) $\displaystyle x^2y=16$

$\displaystyle y^2-x^2+16=0$

3) $\displaystyle x-2y=2$

$\displaystyle y^2-x^2=2x+4$

Any help is greatly appreciated..thanks