Recognize that as \(x\) approaches 4, the numerator \(x^2 - 16\) approaches \$4^2 - 16 = 0\(, and the denominator \)\ln(x - 3)\( approaches \)\ln(1) = 0\(, so this is an indeterminate form \)\frac{0}{0}$ suitable for applying Taylor series expansions.
Expand the numerator \(x^2 - 16\) around \(x = 4\) using the Taylor series (or simply use the linear approximation): \(x^2 - 16 = (4)^2 - 16 + 2 \cdot 4 (x - 4) + \cdots = 0 + 8(x - 4) + \cdots\).
Expand the denominator \(\ln(x - 3)\) around \(x = 4\). Since \(x - 3\) approaches 1, use the expansion of \(\ln(1 + h)\) where \(h = x - 4\): \(\ln(x - 3) = \ln(1 + (x - 4)) = (x - 4) - \frac{(x - 4)^2}{2} + \cdots\).
Substitute these expansions back into the limit expression and simplify by canceling common factors, then evaluate the limit by taking \(x \to 4\) (or equivalently \(h \to 0\)).
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Limits and Limit Evaluation
Limits describe the behavior of a function as the input approaches a particular value. Evaluating limits helps determine the function's value near points where direct substitution may be undefined or indeterminate, such as 0/0 or ∞/∞ forms.
A Taylor series represents a function as an infinite sum of terms calculated from its derivatives at a single point. It approximates functions near that point, allowing simplification of complex expressions to evaluate limits or analyze behavior.
When direct substitution in limits results in indeterminate forms like 0/0, expanding numerator and denominator into Taylor series helps identify leading terms. This approach simplifies the limit evaluation by canceling common factors and revealing the limit's value.