Limits, Continuity & Differentiability
General
Grade 12

Question:

<p>Let f(x) = ( sin x x ∈Z 0 x /∈Z and g(x) =      x2 + 1 x ̸= 0, 2 4 x = 0 5 x = 2 , then:</p>
lim\nx\to 0 g(f(x)) = 4
lim\nx\to 0 f(g(x)) = 0
lim\nx\to 1 f(g(x)) = 0
lim\nx\to 1 g(f(x)) = 5

Step-by-Step Solution

Key Concept: General
<p><strong>1</strong>: Check (A): For x \to 0, x is a small non-integer. Thus f(x) = 0. As x approaches 0,</p> f(x) is identically 0. So g(f(x)) = g(0) = 4. Correct.<p><strong>2</strong>: Check (B): As x \to 0, g(x) = x2 + 1 \to 1. However, for x ̸= 0, g(x) > 1 and is not an</p> integer. Thus f(g(x)) = 0. Correct.<p><strong>3</strong>: Check (C): As x \to 1, g(x) = x2 + 1 \to 2. For x near 1, g(x) is near 2 but not exactly</p> 2 (except at x = 1). In the deleted neighborhood, g(x) is non-integer, so f(g(x)) = 0. Correct.
Correct Answer: (A, B, C)

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