note: x^2 means x ( or whatever variable) to the power of 2

p^2-q^2+r^2-2pr

factor by grouping ( or any other method)

i've tried to factor it into this format: (x-y+z)(x-y-z), but i can't seem to do it. the answer key says that the answer is (p-r+q)(p-r-q), but I don't understand how they got to it.