Precalculus: Concepts Through Functions, A Unit Circle Approach to Trigonometry (3rd Edition)

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We find the left-hand limit as follows: $\lim\limits_{x \to 2^{-}} f(x)=\lim\limits_{x \to 2^{-}} (4-2x) \\=\lim\limits_{x \to 2^{-}} (4) -\lim\limits_{x \to 2^{-}} (2x) \\=4-(2)(2) \\=0$