 These restrictions also apply to the use of these extended real numbers as the limits of sequences or functions. Whenever two sequences or functions both have a finite limit, their sum or difference will have a limit that is the sum or difference of their limits. When one has a finite limit and the other is infinite, then their sum or difference will be determined by the one that is infinite. But when both are infinite, there are problems. We can see that \(1/x^2\), \(2+1/x^2\), and \(1/x^4\) are all functions that go to \(+\infty\) as \(x\) goes to 0. If we add or subtract any of these functions from a function with a finite limit, the resulting function still has limit of \(+\infty\). If we add them to each other in any combination, the result still has limit \(+\infty\). But if we consider their differences, we see that \(1/x^2 - 1/x^2\) has 0 as its limit, \(1/x^2 - 1/x^4\) has \(-\infty\) as its limit, and \(1/x^2 -(2+1/x^2)\) has \(-2\) as its limit. So “\(\infty - \infty\)” is said to be an “indeterminate form” that can’t be evaluated.