Question

(x^2-y^2)/(x-y)=(x-y)/c find c

Answer 1

(x+y)(x-y)/(x-y)=(x-y)/c
x+y=x-y/c
c=x+y/x-y
than rationalise this and you have the answer

Answer 2

I hope this helps
You take the identity of (a²-b²) to expand the first bracket and then simply it.