I found this and everything makes sense.
But I don't understand how CPhill got to 2xh + 2yh = 2ab . I tried working out and expanding the given equation in the problem and using the triangle similarity he provided in an attempt to get what he got, but I don't understand how. Does anyone understand and can explain this part to me? Thank you!
You can use the area formula.
In the original post, there was this equation:
x2 + 2xh + h2 + y2 + 2yh + h2 = x2 + h2 + 2ab + y2 + h2
Subtract x2, h2, y2, and h2 from both sides and you are left with: 2xh + 2yn = 2ab