Chapter 12: Problem 1
Suppose that \(\lim _{x \rightarrow a} f(x)=-3 \quad \lim _{x \rightarrow a} g(x)=0 \quad \lim _{x \rightarrow a} h(x)=8\) Find the value of the given limit. If the limit does not exist, explain why. (a) \(\lim _{x \rightarrow a}[f(x)+h(x)]\) (b) \(\lim _{x \rightarrow a}[f(x)]^{2}\) (c) \(\lim _{x \rightarrow a} \sqrt[3]{h(x)}\) (d) \(\lim _{x \rightarrow a} \frac{1}{f(x)}\) (e) \(\lim _{x \rightarrow a} \frac{f(x)}{h(x)}\) (f) \(\lim _{x \rightarrow a} \frac{g(x)}{f(x)}\) (g) \(\lim _{x \rightarrow a} \frac{f(x)}{g(x)}\) (h) \(\lim _{x \rightarrow a} \frac{2 f(x)}{h(x)-f(x)}\)
Short Answer
Step by step solution
Sum of Limits
Limit of a Function Squared
Limit of a Cube Root
Limit of the Reciprocal
Limit of a Fraction
Limit of a Zero Numerator
Uncertain Fraction
Combining Limits with Adjustments
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Limit Properties
- Sum Property: If you have two functions, say \( f(x) \) and \( h(x) \), and you are supposed to find the limit of their sum as \( x \) approaches a particular value, you simply add their individual limits. For example, \( \lim_{x \rightarrow a} (f(x) + h(x)) = \lim_{x \rightarrow a} f(x) + \lim_{x \rightarrow a} h(x) \).
- Product Property: Similar to addition, the limit of a product is the product of the limits. Meaning, \( \lim_{x \rightarrow a} [f(x) \cdot g(x)] = \lim_{x \rightarrow a} f(x) \cdot \lim_{x \rightarrow a} g(x) \).
- Difference and Quotient Properties: Limits of differences and quotients follow similar rules, provided the denominator is not zero in case of quotients.
Division by Zero
- If you have a function \( \frac{f(x)}{g(x)} \) and \( \lim_{x \rightarrow a} g(x) = 0 \) while \( \lim_{x \rightarrow a} f(x) eq 0 \), the limit does not exist in the traditional sense, because the result is either infinity, negative infinity, or an indeterminate form.
- For example, \( \lim_{x \rightarrow a} \frac{f(x)}{g(x)} = \text{DNE (does not exist), if } g(x) = 0 \).
Fractional Limits
- Direct Substitution: First, try to substitute the values directly. If the denominator isn't zero, directly compute the fraction using the limits of the numerator and the denominator.
- Standard Form: If direct substitution leads to quotients like \( \frac{0}{0} \), further analysis is needed, often involving algebraic manipulation or simplifications to resolve the indeterminate form.
- Evaluation of Non-Zero Denominator: Ensure the denominator is non-zero for limits to exist in a fractional context, like \( \lim_{x \rightarrow a} \frac{f(x)}{h(x)} = \frac{-3}{8} \) in the given example.
Function Operations
- Addition/Subtraction: When adding or subtracting functions under limits, break them into simpler parts using basic limit properties.
- Multiplication: Similarly, for multiplication, use the product of limits property. Keep in mind possible zero outcomes for more complex evaluation.
- Root and Power Functions: When dealing with power functions or roots, apply limits into \( [f(x)]^n \) or \( \sqrt[n]{f(x)} \), as shown by the cube root of 8 yielding 2.
- Reciprocals and Ratios: When working with reciprocals or ratios, ensure the denominator isn’t zero, particularly when evaluating as seen in the \( \frac{1}{f(x)} \) example, where checking \( f(x) eq 0 \) ensures the limit exists.