Question #N459
Which of the following is equivalent to the expression $(x^2+1)(x^2-1)$?
A. x^4 - 1
B. x^4 + 1
C. x^4 + 2x^2 + 1
D. x^4 - 2x^2 + 1
Correct Answer is: A
This expression is in the form of the difference of squares: (a + b)(a - b) = a^2 - b^2. In this case, a = x^2 and b = 1. Therefore, (x^2 + 1)(x^2 - 1) = (x^2)^2 - 1^2 = x^4 - 1.