Estimating Limit Values from Tables
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AP Calculus BC › Estimating Limit Values from Tables
Values of a function $$g$$ are given for selected values of $$x$$ near -4. For $$x$$ values of -4.1, -4.01, and -4.001, the $$g(x)$$ values are 500, 5000, and 50000. For $$x$$ values of -3.999, -3.99, and -3.9, the $$g(x)$$ values are 49999, 4999, and 499. The function is undefined at $$x=-4$$. What is the best estimate for $$\lim_{x \to -4} g(x)$$?
0
$$\infty$$
50000
The limit does not exist.
Explanation
The correct answer is $$\infty$$. As $$x$$ approaches -4 from the left, the values of $$g(x)$$ are increasing without bound. As $$x$$ approaches -4 from the right, the values of $$g(x)$$ are also increasing without bound. Since both sides approach positive infinity, the limit is considered to be $$\infty$$. Choice A is one of the data points. Choice D is incorrect because the behavior from both sides is the same (approaching $$\infty$$).
The function $$h$$ is continuous. A table of values for $$h(x)$$ is given: for $$x$$ values of -10, -100, -1000, and -10000, the corresponding $$h(x)$$ values are -0.4, -0.49, -0.499, and -0.4999. What is the best estimate for $$\lim_{x \to -\infty} h(x)$$?
-0.4
The limit does not exist.
0
-0.5
Explanation
The correct answer is -0.5. The limit as $$x \to -\infty$$ describes the end behavior of the function as $$x$$ decreases without bound. The table shows that as $$x$$ becomes more negative, the values of $$h(x)$$ get closer to -0.5. Choice C is the first value in the table. Choice B is a common limit value but not supported by the data. Choice D is incorrect as the values are approaching a single number.
The functions $$f$$ and $$g$$ are continuous. A table of values near $$x=-3$$ is given. For $$x$$ values of -3.1, -3.01, and -3.001, the $$f(x)$$ values are 11.7, 11.97, and 11.997, and the $$g(x)$$ values are 1.9, 1.99, and 1.999. For $$x$$ values of -2.999, -2.99, and -2.9, the $$f(x)$$ values are 12.003, 12.03, and 12.3, and the $$g(x)$$ values are 2.001, 2.01, and 2.1. What is the best estimate for $$\lim_{x \to -3} \frac{f(x)}{g(x)}$$?
6
10
The limit does not exist.
14
Explanation
The correct answer is 6. From the table, as $$x \to -3$$, $$f(x) \to 12$$ and $$g(x) \to 2$$. Using the quotient property of limits, $$\lim_{x \to -3} \frac{f(x)}{g(x)} = \frac{\lim_{x \to -3} f(x)}{\lim_{x \to -3} g(x)} = \frac{12}{2} = 6$$. Choice B is the sum of the limits. Choice C is the sum of the function values at x=-3 (if they were given). Choice D is incorrect because the individual limits exist and the denominator's limit is not zero.
Values of a function $$h$$ are given for selected values of $$x$$ near 3. For $$x$$ values of 2.9, 2.99, and 2.999, the corresponding $$h(x)$$ values are -1.5, -1.95, and -1.995. For $$x$$ values of 3.001, 3.01, and 3.1, the corresponding $$h(x)$$ values are -3.998, -3.98, and -3.8. The function is undefined at $$x=3$$. What is the best estimate for $$\lim_{x \to 3^+} h(x)$$?
The limit does not exist.
-2
3
-4
Explanation
The correct answer is -4. The notation $$x \to 3^+$$ indicates the limit as $$x$$ approaches 3 from the right side (values greater than 3). The table shows that for $$x$$ values of 3.001, 3.01, and 3.1, the values of $$h(x)$$ are approaching -4. Choice A is the left-hand limit. Choice C is the value $$x$$ is approaching. Choice D is incorrect because the one-sided limit exists.
A differentiable function $$f$$ satisfies $$f(2) = 8$$. A table of values for the difference quotient $$\frac{f(2+h)-f(2)}{h}$$ is given. For $$h$$ values of -0.1, -0.01, and -0.001, the quotient's values are 3.9, 3.99, and 3.999. For $$h$$ values of 0.001, 0.01, and 0.1, the quotient's values are 4.001, 4.01, and 4.1. What is the best estimate for $$\lim_{h \to 0} \frac{f(2+h)-f(2)}{h}$$?
4
The limit does not exist.
0
8
Explanation
The correct answer is 4. The expression in the limit is the definition of the derivative of $$f$$ at $$x=2$$, i.e., $$f'(2)$$. The table directly provides values of this difference quotient as $$h$$ approaches 0 from the left and the right. As $$h \to 0^-$$, the quotient approaches 4. As $$h \to 0^+$$, the quotient approaches 4. Since both one-sided limits are equal, the limit is 4. Choice C is the value of $$f(2)$$.
The functions $$f$$ and $$g$$ are continuous. A table of values near $$x=4$$ is given. For $$x$$ values of 3.9, 3.99, and 3.999, the $$f(x)$$ values are 6.8, 6.98, and 6.998, and the $$g(x)$$ values are -2.2, -2.02, and -2.002. For $$x$$ values of 4.001, 4.01, and 4.1, the $$f(x)$$ values are 7.002, 7.02, and 7.2, and the $$g(x)$$ values are -1.998, -1.98, and -1.8. What is the best estimate for $$\lim_{x \to 4} (f(x) + g(x))$$?
The limit does not exist.
4.6
5
9
Explanation
The correct answer is 5. From the table, as $$x \to 4$$, $$f(x) \to 7$$ and $$g(x) \to -2$$. Using the sum property of limits, $$\lim_{x \to 4} (f(x) + g(x)) = \lim_{x \to 4} f(x) + \lim_{x \to 4} g(x) = 7 + (-2) = 5$$. Choice B is the difference of the limits. Choice C is the sum of the first values in the table. Choice D is incorrect because both individual limits exist.
Values of a function $$f$$ are given for selected values of $$x$$ near 2. The table shows that for $$x$$ values of 1.9, 1.99, and 1.999, the corresponding $$f(x)$$ values are 4.71, 4.97, and 4.997. For $$x$$ values of 2.001, 2.01, and 2.1, the corresponding $$f(x)$$ values are 5.003, 5.03, and 5.31. The value of $$f(2)$$ is 7. What is the best estimate for $$\lim_{x \to 2} f(x)$$?
5.003
7
5
The limit does not exist.
Explanation
The correct answer is 5. As $$x$$ approaches 2 from the left ($$x=1.9, 1.99, 1.999$$), $$f(x)$$ approaches 5. As $$x$$ approaches 2 from the right ($$x=2.001, 2.01, 2.1$$), $$f(x)$$ also approaches 5. Since the left-hand and right-hand limits are equal, the limit is 5. The value $$f(2)=7$$ is irrelevant to the value of the limit. Choice B is the value of the function at $$x=2$$, not the limit. Choice C is a single value from the table, not the limit. Choice D is incorrect because the left and right limits both approach 5.
Values of a function $$g$$ are given for selected values of $$x$$ near -1. For $$x$$ values of -1.1, -1.01, and -1.001, the corresponding $$g(x)$$ values are 8.8, 8.98, and 8.998. For $$x$$ values of -0.999, -0.99, and -0.9, the corresponding $$g(x)$$ values are 7.002, 7.02, and 7.2. The value of $$g(-1)$$ is 3. What is the best estimate for $$\lim_{x \to -1^-} g(x)$$?
3
The limit does not exist.
9
7
Explanation
The correct answer is 9. The notation $$x \to -1^-$$ indicates the limit as $$x$$ approaches -1 from the left side (values less than -1). The table shows that for $$x$$ values of -1.1, -1.01, and -1.001, the values of $$g(x)$$ are approaching 9. Choice A is the value of the function at $$x=-1$$. Choice B is the right-hand limit, not the left-hand limit. Choice D is incorrect because the one-sided limit exists.
The function $$f$$ is continuous. A table of values for $$f(x)$$ is given: for $$x$$ values of 10, 100, 1000, and 10000, the corresponding $$f(x)$$ values are 3.1, 3.01, 3.001, and 3.0001. What is the best estimate for $$\lim_{x \to \infty} f(x)$$?
The limit does not exist.
3
0
3.1
Explanation
The correct answer is 3. The limit as $$x \to \infty$$ describes the end behavior of the function as $$x$$ increases without bound. The table shows that as $$x$$ gets larger, the values of $$f(x)$$ get closer and closer to 3. Choice A is a common limit value but not supported by the data. Choice C is the first value in the table. Choice D is incorrect as the values are approaching a single number.
The functions $$f$$ and $$g$$ are continuous. A table of values near $$x=4$$ is given. For $$x$$ values of 3.9, 3.99, and 3.999, the $$f(x)$$ values are 6.8, 6.98, and 6.998, and the $$g(x)$$ values are -2.2, -2.02, and -2.002. For $$x$$ values of 4.001, 4.01, and 4.1, the $$f(x)$$ values are 7.002, 7.02, and 7.2, and the $$g(x)$$ values are -1.998, -1.98, and -1.8. What is the best estimate for $$\lim_{x \to 4} (f(x) \cdot g(x))$$?
5
-14
-14.96
The limit does not exist.
Explanation
The correct answer is -14. From the table, as $$x \to 4$$, $$f(x) \to 7$$ and $$g(x) \to -2$$. Using the product property of limits, $$\lim_{x \to 4} (f(x) \cdot g(x)) = (\lim_{x \to 4} f(x)) \cdot(\lim_{x \to 4} g(x)) = 7 \cdot(-2) = -14$$. Choice B is the sum of the limits. Choice C is the product of the first values in the table. Choice D is incorrect because both individual limits exist.