[ASK] Reflection of a Line by Another Line

[Monoxdifly]

The reflection of the line 5x - 7y - 13 = 0 by the line y = -x is ...
A. 7x + 5y - 13 = 0
B. 7x + 5y + 13 = 0
C. 7x - 5y - 13 = 0
D. 7x - 5y + 13 = 0
E. 7y + 5x + 13 = 0

This one I totally have no idea. Like, at all.

 

[MarkFL]

If we let:

$$y=-x$$

and

$$x=-y$$

in the given line, what do we obtain?

 

[Monoxdifly]

-5y + 7x - 13 = 0?

 

[MarkFL]

-5y + 7x - 13 = 0?

Correct. :)

 

[Monoxdifly]

I can't believe that out of the 4 questions I asked tonight, the one I found the hardest was the one with the simplest step.