Question

Show that the expression (x+y)(x-y)-14x+49 may be written as the difference of two squares.

Answer 1

For
(a-b)(a+b)=a^2-b^2

x^2-y^2-14x+49
x^2-14x+49-y^2
(x-7)^2-y^2
(x-7-y)(x-7+y)
or
(x-y-7)(x+y-7)