Question 34745
Can you see this expression as the difference of two squares?

{{{x^4 - 1 = (x^2)^2 - (1)^2}}}

The difference of two squares is factorable thus:
{{{a^2 - b^2 = (a + b)(a - b)}}} Apply this to your problem.

{{{(x^2)^2 - (1)^2 = (x^2 + 1)(x^2 - 1)}}} Notice that the second parentheses is again the difference of two squares and can be factored as before.

{{{(x^2 - 1) = (x + 1)(x - 1)}}}

Putting it all together, we have:
{{{x^4 - 1 = (x^2 + 1)(x + 1)(x - 1)}}}