Got the question from Khan academy under the linked chapter.
Why is it that we need to establish that “$x$ is not equal $-3$” before we cancel after factoring?
I was under the impression we can cancel any algebra that we can simplify.
2026-04-07 11:14:06.1775560446
Calculus: limits, factorisation and cancelling because $x \neq -3$
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It is not the act of canceling that requires us to establish/require that $x$ is not equal to $-3$, but the fact that $x+3$ appears as the denominator of a fraction. After canceling, we have to remember that the formula we get is valid only for $x \neq -3$, even though $x+3$ doesn't appear as a denominator anymore.