How to factor y^2 - 49 + 14x - x^2 with (y - x + 7)(y + x - 7) being the answer?

Answer 1

y^2-x^2+14x-49

=y^2 -(x^2-14x+49)

=y^2 -(x-7)^2

use the formula a^2-b^2 =(a-b)(a+b)

with a=y and b=x-7

= (y-(x-7))(y+(x-7))

=(y-x+7)(y+x-7)