The factors of the expression x^2 - 49 = 0 are as follows
(x + 7) (x - 7) = 0
The number 49 is a perfect square, and therefore the roots are either a negative 7 or a positive 7.
So the factores would be x + 7 or x - 7. That is,
When x + 7 = 0
Then x = -7
When x - 7 = 0
Then x = 7
The factors of the expression therefore are
(x + 7) and (x - 7)