Answer:
(x - 10)(x + 10)
Explanation:
x^2 - 100 = (x - 10)(x + 10) <==
what u have here is a difference of squares.....x^2 is a perfect square(x)^2 and 100 is a perfect square (10)^2
u see : x^2 - 100 = (x)^2 - (10)^2 = (x - 10)(x + 10)
a^2 - b^2 = (a - b)(a + b)
now a difference of squares cannot be done if it was x^2 + 100