You can put this solution on YOUR website! I'll assume you are asking the following expression factored:
x^4-625y^4
Can be written as a "difference of squares":
(x^2)^2 - (25y^2)^2
(x^2 - 25y^2)(x^2 + 25y^2)
The left expression can be also be written as a "difference of squares":
(x^2 - (5y)^2)(x^2 + 25y^2)
which expands to:
(x^2 - 5y)(x^2 + 5y)(x^2 + 25y^2)
