volume_mute
What Is x − (−∞)?
publish date: 2026/05/23 22:07:22.089459 UTC
volume_mute
For \(x \in \mathbb{R}\), what is \(x - (-\infty)\)?
Correct Answer
\(+\infty\)
Explanation
\(x - (-\infty) = x + \infty = +\infty\). Subtracting a negative infinity from a finite number is equivalent to adding positive infinity, giving \(+\infty\). These rules follow a logical pattern consistent with limits of sequences: if \(a_n \to -\infty\) then \(x - a_n \to +\infty\).
Reference
Introduction to Differential Calculus (Systematic Studies with Engineering Applications for Beginners) - 2012