Candidates Test

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AP Calculus BC › Candidates Test

Questions 1 - 10
1

A continuous function $r$ on $-4,2$ has critical points $x=-2,1$ and values $r(-4)=3,r(-2)=0,r(1)=-1,r(2)=2$; where is the absolute minimum?

Cannot be determined from given information

$x=2$

$x=1$

$x=-4$

$x=-2$

Explanation

This problem tests the Candidates Test for finding the absolute minimum on the interval [-4,2]. The Candidates Test tells us that absolute extrema of continuous functions on closed intervals must occur at critical points or endpoints. Our candidates are the critical points x = -2 and x = 1, plus the endpoints x = -4 and x = 2. Comparing function values: r(-4) = 3, r(-2) = 0, r(1) = -1, and r(2) = 2, we see that r(1) = -1 is the smallest value. Students might incorrectly choose x = -2 since it has value 0, but the critical point x = 1 yields the actual minimum. Remember the complete process: list all critical points within the interval, include both endpoints, evaluate at each candidate, and identify the smallest value for the absolute minimum.

2

For continuous $q$ on $-3,3$ with critical points $x=-1,2$ and values $q(-3)=0,q(-1)=4,q(2)=5,q(3)=1$, where is the absolute maximum?

$x=2$

$x=-3$

$x=3$

$x=-1$

Cannot be determined from given information

Explanation

This question applies the Candidates Test to find the absolute maximum of q on [-3,3]. The Candidates Test guarantees that for a continuous function on a closed interval, the absolute maximum and minimum occur at critical points or endpoints. We must check the critical points x = -1 and x = 2, plus the endpoints x = -3 and x = 3. Evaluating at all candidates: q(-3) = 0, q(-1) = 4, q(2) = 5, and q(3) = 1, we find that q(2) = 5 is the largest value. Some students might select x = -1 because it's the first critical point with a large value, but we must compare all candidates. The foolproof method: identify critical points, add both endpoints, evaluate the function at each candidate, and select the one with the maximum value.

3

A continuous function $g$ on $0,6$ has critical points $x=2,5$ and values $g(0)=3,g(2)=-1,g(5)=2,g(6)=0$; where is the absolute minimum?

$x=6$

$x=5$

Cannot be determined from given information

$x=0$

$x=2$

Explanation

This problem applies the Candidates Test to locate the absolute minimum of a continuous function on [0,6]. The Candidates Test requires checking all critical points (where the derivative is zero or undefined) and endpoints when finding absolute extrema on closed intervals. Our candidates are the critical points x = 2 and x = 5, plus the endpoints x = 0 and x = 6. Comparing the function values: g(0) = 3, g(2) = -1, g(5) = 2, and g(6) = 0, we find that g(2) = -1 is the smallest value. Students might incorrectly choose x = 0 thinking endpoints always give extrema, but critical points can produce more extreme values. The key checklist: identify all critical points, include both endpoints, evaluate the function at each candidate, and select the smallest (for minimum) or largest (for maximum) value.

4

For continuous $u$ on $2,8$ with critical points $x=4,7$ and values $u(2)=1, u(4)=-2, u(7)=0, u(8)=-3$, where is the absolute minimum?

$x=2$

$x=4$

$x=8$

Cannot be determined from given information

$x=7$

Explanation

This question tests the Candidates Test for finding the absolute minimum of $u$ on $[2,8]$. The Candidates Test tells us that for continuous functions on closed intervals, absolute extrema must occur at critical points or endpoints—these are the only candidates we need to check. We have critical points at $x=4$ and $x=7$, and endpoints at $x=2$ and $x=8$. Comparing values: $u(2)=1$, $u(4)=-2$, $u(7)=0$, and $u(8)=-3$, we find that $u(8)=-3$ is the smallest value. Some might choose $x=4$ since it's a critical point with a negative value, but the endpoint $x=8$ has an even smaller value. Always remember: check all critical points AND both endpoints, then select the location with the minimum function value.

5

For continuous $h$ on $-3,3$, critical points are $x=-2,1$ with $h(-3)=4,h(-2)=2,h(1)=6,h(3)=5$. Where is the absolute maximum?

At $x=3$

At $x=1$

At $x=-3$

At $x=-2$ and $x=1$ (a tie)

At $x=-2$

Explanation

The Candidates Test is a method to find absolute extrema of a continuous function on a closed interval by evaluating the function at critical points and endpoints. We check critical points because they may represent local maxima that could be the global maximum on the interval. Endpoints need evaluation as the function might reach its highest value at the start or end of the domain. This comparison ensures we don't miss the absolute maximum by overlooking any candidate. One tempting distractor is x=-3 with h(-3)=4, but it fails as it's less than h(1)=6, demonstrating incomplete comparison. Always list and evaluate the function at: both endpoints and all critical points within the interval.

6

A continuous function $t$ on $-2,6$ has critical points $x=0,5$ and values $t(-2)=-1,t(0)=3,t(5)=3,t(6)=2$; where is the absolute maximum?

$x=0$ and $x=5$

$x=5$

$x=-2$

$x=0$

$x=6$

Explanation

This problem applies the Candidates Test to find where the absolute maximum occurs for t on [-2,6]. The Candidates Test guarantees that absolute extrema of continuous functions on closed intervals occur at critical points or endpoints. Our candidates include critical points x = 0 and x = 5, plus endpoints x = -2 and x = 6. Evaluating at all candidates: t(-2) = -1, t(0) = 3, t(5) = 3, and t(6) = 2, we see that both t(0) = 3 and t(5) = 3 equal the maximum value. Students might think only one location can be the maximum, but when multiple candidates achieve the same maximum value, all such locations are correct. The complete method: list critical points and endpoints, evaluate at each, and identify all locations achieving the maximum value.

7

For continuous $f$ on $-2,4$ with critical points $x=0,3$ and values $f(-2)=1,f(0)=5,f(3)=2,f(4)=4$, where is the absolute maximum?​

At $x=3$

At $x=0$

At $x=4$

At $x=-2$

It cannot be determined without $f'(x)$

Explanation

This problem requires applying the Candidates Test to find the absolute maximum of a continuous function on a closed interval. For any continuous function on a closed interval, the absolute extrema must occur either at critical points (where the derivative is zero or undefined) or at the endpoints of the interval. We must check all candidates: the critical points at x = 0 and x = 3, and the endpoints at x = -2 and x = 4. Evaluating at each candidate: f(-2) = 1, f(0) = 5, f(3) = 2, and f(4) = 4, we see that the largest value is 5, occurring at x = 0. Some students might incorrectly choose an endpoint thinking extrema must occur there, but critical points can also be locations of absolute extrema. The Candidates Test checklist: (1) verify continuity on the closed interval, (2) identify all critical points and endpoints, (3) evaluate the function at each candidate, and (4) compare values to find the absolute maximum and minimum.

8

For continuous $s$ on $-4,0$ with critical points $x=-3,-1$, given $s(-4)=2,s(-3)=2,s(-1)=-5,s(0)=-1$, where is the absolute minimum?

$x=-1$

$x=-3$ (since it is a critical point)

$x=-4$

$x=0$

$x=-3$

Explanation

This question applies the Candidates Test to find the absolute minimum on [-4,0]. The Candidates Test tells us that absolute extrema for continuous functions on closed intervals must occur at critical points or endpoints. We need to check endpoints x = -4 and x = 0, along with critical points x = -3 and x = -1. The function values are: s(-4) = 2, s(-3) = 2, s(-1) = -5, and s(0) = -1. Since s(-1) = -5 is the smallest value, the absolute minimum occurs at x = -1. Choice E incorrectly focuses on x = -3 being a critical point as if that status alone determines extrema, but we must compare actual function values at all candidates. The systematic candidates approach: list all critical points within the interval, add both endpoints, evaluate the function at each candidate, and identify the location with the minimum value.

9

For continuous $u$ on $-2,6$ with critical points $x=2,5$, given $u(-2)=0,u(2)=4,u(5)=3,u(6)=5$, where is the absolute maximum?​

$x=2$

$x=5$

$x=6$

$x=-2$

There is no absolute maximum on $[-2,6]$.

Explanation

This problem requires applying the Candidates Test to find the absolute maximum of a continuous function on a closed interval. The Candidates Test guarantees that absolute extrema occur at critical points or endpoints for continuous functions on closed intervals. We examine four candidates: endpoints x = -2 and x = 6, and critical points x = 2 and x = 5. Function values at these points are: u(-2) = 0, u(2) = 4, u(5) = 3, and u(6) = 5. The largest value is u(6) = 5, so the absolute maximum occurs at the endpoint x = 6. A common mistake would be assuming the maximum must occur at a critical point like x = 2 where u(2) = 4, but endpoints can also produce absolute extrema. The foolproof candidates checklist is: identify all critical points in the interval, include both endpoints as candidates, evaluate the function at all candidates, then select the location with the maximum value.

10

A continuous function $t$ on $0,5$ has critical points $x=1,3$ with $t(0)=2,t(1)=2,t(3)=-1,t(5)=0$; where is the absolute minimum?​

At $x=3$

At $x=5$

At $x=1$

At $x=0$ or $x=1$ because $t(0)=t(1)$

At $x=0$

Explanation

This problem demonstrates the Candidates Test for locating the absolute minimum of a continuous function on [0, 5]. The Candidates Test principle states that absolute extrema of continuous functions on closed intervals occur at critical points or endpoints—nowhere else. Our candidates are critical points x = 1 and x = 3, plus endpoints x = 0 and x = 5. Computing values: t(0) = 2, t(1) = 2, t(3) = -1, and t(5) = 0, we find the minimum value is -1 at x = 3. Choice E incorrectly focuses on the equal values at x = 0 and x = 1, but equal function values don't determine extrema—we need the smallest value overall. Apply the Candidates Test systematically: list all candidates, evaluate the function at each, then identify where the minimum occurs.

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