First you have to multiply through the parentheses on the left. Then you have to bring all the terms that are related to $x$ to the left side of the...
In post #16 we had the translation by $d=2$ and the new reflection line is $y=\frac{d}{2}$. But in that we case we had that the first reflection line...
When we have the point $(x,y)$ after the reflection we get the point $(x,-y)$. After a perpendicular translation we get the point $(x,y')$, for some...