I've just started reading Spivak's Calculus text (4th ed.) and am having some trouble on one of the exercises. The problem asks me to prove that if $|x-x_0|<\frac{\epsilon}{2}$ and $|y-y_0|<\frac{\epsilon}{2}$, then $|x-y-(x_0-y_0)|< \epsilon$. I've proven that it implies that $|x+y-(x_0 + y_0)|<\epsilon$ by adding the two given inequalities and using the addition triangle inequality for absolute value, but I can't find a way to apply the subtraction triangle inequality on this problem. Any help would be appreciated, thanks.
2026-03-30 03:50:11.1774842611
Proving an Absolute Value Inequality
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Hints:
$$|x-y-(x_0-y_0)|=|x-x_0-(y-y_0)|\le|x-x_0|+|y-y_0|\ldots$$