Working With the Intermediate Value Theorem

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AP Calculus BC › Working With the Intermediate Value Theorem

Questions 1 - 10
1

Let $r$ be continuous on $-4,-1$ with $r(-4)=3$ and $r(-1)=-6$. Does IVT guarantee some $c$ with $r(c)=-2$?

Yes, because $r$ is continuous on $[-4,-1]$ and $-2$ is between $r(-4)$ and $r(-1)$.

No, because $-2$ is not between $-4$ and $-1$.

Yes, because $r$ is continuous at $x=-4$ and $x=-1$.

Yes, because $r(-4)>0$.

No, because IVT requires $r(-4)=0$.

Explanation

This problem requires applying the Intermediate Value Theorem to find if r(c) = -2 has a solution. The IVT states that for a continuous function on [a,b], any value k between f(a) and f(b) is attained by the function. Given r is continuous on [-4,-1] with r(-4) = 3 and r(-1) = -6, we check if -2 is between 3 and -6. Since -6 < -2 < 3, the value -2 lies between r(-4) and r(-1), so IVT guarantees there exists c in [-4,-1] where r(c) = -2. Choice A incorrectly compares -2 with the domain values -4 and -1, but IVT requires comparing with the range values at the endpoints. Remember: IVT needs (1) continuity on [a,b], (2) target value between f(a) and f(b), not between a and b.

2

A continuous function $g$ on $-2,3$ satisfies $g(-2)=4$ and $g(3)=-1$. Does IVT guarantee some $c$ with $g(c)=2$?

No, because $g$ might not be differentiable on $[-2,3]$.

Yes, because $g$ is continuous on $[-2,3]$ and $2$ is between $g(-2)$ and $g(3)$.

Yes, because $g(-2)>g(3)$.

Yes, because $g$ is defined at $-2$ and $3$.

No, because $2$ is not between $-2$ and $3$.

Explanation

This problem requires applying the Intermediate Value Theorem to find if g(c) = 2 has a solution. The IVT applies when a function is continuous on a closed interval [a,b] and we're looking for a value k that lies between f(a) and f(b). Given that g is continuous on [-2,3] with g(-2) = 4 and g(3) = -1, we need to check if 2 is between 4 and -1. Since -1 < 2 < 4, the value 2 is indeed between g(-2) and g(3), so IVT guarantees there exists at least one c in [-2,3] where g(c) = 2. Choice B incorrectly confuses the domain interval [-2,3] with the range values—the target value 2 needs to be between the function values, not the x-values. Remember the IVT checklist: continuous function, closed interval, and target value between endpoint function values.

3

Let $p$ be continuous on $-1,2$ with $p(-1)=-5$ and $p(2)=1$. Does IVT guarantee some $c$ with $p(c)=-3$?

Yes, because $p(-1)$ and $p(2)$ have opposite signs.

Yes, because $p$ is differentiable on $[-1,2]$.

No, because $-3$ is not between $-1$ and $2$.

No, because IVT applies only to polynomials.

Yes, because $p$ is continuous on $[-1,2]$ and $-3$ is between $p(-1)$ and $p(2)$.

Explanation

This problem asks you to apply the Intermediate Value Theorem to determine if p(c) = -3 has a solution. The IVT guarantees that if a function is continuous on [a,b] and k is any value between f(a) and f(b), then f(c) = k for some c in [a,b]. Given that p is continuous on [-1,2] with p(-1) = -5 and p(2) = 1, we need to verify that -3 is between -5 and 1. Since -5 < -3 < 1, the value -3 is indeed between p(-1) and p(2), so IVT guarantees a solution exists. Choice D incorrectly thinks -3 needs to be between the x-values -1 and 2, but IVT requires the target value to be between the y-values at the endpoints. For IVT success: (1) verify continuity, (2) identify endpoint values, (3) check if target lies between them.

4

Suppose $h$ is continuous on $0,6$ with $h(0)=10$ and $h(6)=10$. Does IVT guarantee a solution to $h(x)=0$ on $0,6$?

Yes, because $h(0)=h(6)$.

No, because $h$ may not be increasing on $[0,6]$.

Yes, because $h$ is continuous on $[0,6]$.

No, because $0$ is not between $h(0)$ and $h(6)$.

Yes, because $h$ is continuous at $x=0$ and $x=6$.

Explanation

This question tests whether IVT can guarantee a root when the function has the same value at both endpoints. The IVT states that for a continuous function on [a,b], if k is between f(a) and f(b), then f(c) = k has a solution. Here, h is continuous on [0,6] with h(0) = 10 and h(6) = 10, and we want to know if h(x) = 0 has a solution. Since both endpoint values equal 10, the only value "between" h(0) and h(6) is 10 itself, so 0 is not between the endpoint values. Choice C is tempting because it correctly identifies that h(0) = h(6), but this equality doesn't help us apply IVT for finding where h(x) = 0. The IVT checklist requires: continuity (✓), closed interval (✓), but target value between endpoints (✗).

5

Let $f$ be continuous on $1,5$ with $f(1)=-2$ and $f(5)=7$. Does IVT guarantee a solution to $f(x)=0$?

Yes, because $f(1)$ and $f(5)$ are defined on $[1,5]$.

No, because $f(1)\ne f(5)$.

Yes, because $f$ is continuous on $[1,5]$ and $0$ is between $f(1)$ and $f(5)$.

No, because IVT requires $f(1)=0$ or $f(5)=0$.

Yes, because $f$ is continuous at $x=1$ and $x=5$.

Explanation

This question tests your ability to apply the Intermediate Value Theorem (IVT) to determine if a function has a root. The IVT states that if f is continuous on [a,b] and k is any value between f(a) and f(b), then there exists at least one c in [a,b] where f(c) = k. Here, f is continuous on [1,5], f(1) = -2, and f(5) = 7, so we need to check if 0 is between -2 and 7. Since -2 < 0 < 7, the value 0 is indeed between f(1) and f(5), so IVT guarantees there exists some c in [1,5] where f(c) = 0. Choice B is incorrect because merely having defined values at the endpoints isn't sufficient—we need continuity and the target value must be between the endpoint values. When applying IVT, always verify: (1) continuity on the closed interval, (2) the target value lies between the function values at the endpoints.

6

Let $v$ be continuous on $5,10$ with $v(5)=-9$ and $v(10)=0$. Does IVT guarantee some $c$ with $v(c)=1$?

No, because $v$ might not be increasing on $[5,10]$.

Yes, because $v(10)=0$.

Yes, because $v(5)<v(10)$.

No, because $1$ is not between $v(5)$ and $v(10)$.

Yes, because $v$ is continuous on $[5,10]$.

Explanation

This problem requires determining whether IVT guarantees v(c) = 1 when one endpoint is zero. The IVT applies when a continuous function on [a,b] takes a value k that lies between f(a) and f(b). Given v is continuous on [5,10] with v(5) = -9 and v(10) = 0, we check if 1 is between these values. Since -9 < 0 < 1, we see that 1 is not between v(5) and v(10)—it exceeds both endpoint values. Choice B incorrectly thinks having v(10) = 0 helps guarantee v(c) = 1, but the zero at an endpoint doesn't extend the range of guaranteed values beyond [v(5), v(10)]. Remember the IVT checklist: continuous function (✓), closed interval (✓), target between endpoints (✗ since 1 > 0 > -9).

7

Suppose $s$ is continuous on $0,2$ with $s(0)=-1$ and $s(2)=5$. Does IVT guarantee a solution to $s(x)=7$ on $0,2$?

No, because $7$ is not between $s(0)$ and $s(2)$.

No, because $s$ might not be differentiable on $[0,2]$.

Yes, because $s$ is defined at $0$ and $2$.

Yes, because $s$ is continuous on $[0,2]$.

Yes, because $s(0)$ and $s(2)$ have opposite signs.

Explanation

This question tests whether IVT guarantees a solution to s(x) = 7 when the target exceeds both endpoint values. The IVT applies when a continuous function on [a,b] takes on any value k between f(a) and f(b). Here, s is continuous on [0,2] with s(0) = -1 and s(2) = 5, and we seek s(x) = 7. To check if 7 is between the endpoint values: we have -1 < 5 < 7, so 7 is not between s(0) and s(2)—it exceeds both values. Choice C incorrectly focuses on the signs of the endpoint values, but having opposite signs only helps when seeking a zero, not when seeking 7. The IVT checklist requires: continuous function (✓), closed interval (✓), but target between endpoints (✗ since 7 > 5 > -1).

8

Let $t$ be continuous on $3,8$ with $t(3)=12$ and $t(8)=-4$. Does IVT guarantee some $c$ with $t(c)=6$?

Yes, because $t$ is continuous on $[3,8]$ and $6$ is between $t(3)$ and $t(8)$.

Yes, because $t$ has values at $x=3$ and $x=8$.

No, because $t(8)$ is negative.

Yes, because $t(3)$ is positive.

No, because $6$ is not between $3$ and $8$.

Explanation

This problem asks you to apply the Intermediate Value Theorem to determine if t(c) = 6 has a solution. The IVT guarantees that a continuous function on [a,b] attains every value between f(a) and f(b). Given t is continuous on [3,8] with t(3) = 12 and t(8) = -4, we need to verify that 6 is between these endpoint values. Since -4 < 6 < 12, the value 6 is indeed between t(3) and t(8), so IVT guarantees there exists at least one c in [3,8] where t(c) = 6. Choice A incorrectly thinks 6 needs to be between the x-values 3 and 8, but IVT compares the target with the y-values at endpoints. For successful IVT application: (1) confirm continuity, (2) find endpoint function values, (3) verify target lies between them.

9

A continuous function $q$ on $2,9$ satisfies $q(2)=-8$ and $q(9)=-1$. Does IVT guarantee a solution to $q(x)=0$ on $2,9$?

No, because $0$ is not between $q(2)$ and $q(9)$.

Yes, because $q(2)$ and $q(9)$ are both negative.

Yes, because $q$ is defined on $[2,9]$.

No, because $q$ might have a local maximum.

Yes, because $q$ is continuous on $[2,9]$.

Explanation

This question tests whether IVT can guarantee a zero of q when both endpoint values are negative. The IVT applies when we have a continuous function on [a,b] and seek a value k that lies between f(a) and f(b). Here, q is continuous on [2,9] with q(2) = -8 and q(9) = -1, and we want q(x) = 0. To check if 0 is between the endpoint values: since both -8 and -1 are negative, we have -8 < -1 < 0, meaning 0 is not between q(2) and q(9). Choice C is incorrect because having both endpoint values negative actually prevents 0 from being between them—IVT cannot guarantee a root in this case. The IVT checklist: continuous function (✓), closed interval (✓), target between endpoints (✗ since 0 > both -8 and -1).

10

If $h$ is continuous on $0,3$ with $h(0)=5$ and $h(3)=9$, does IVT guarantee a solution to $h(x)=7$?

Yes, because $h$ is differentiable on $[0,3]$.

No, because IVT only guarantees values between $0$ and $3$.

Yes, because $7$ lies between $h(0)$ and $h(3)$ and $h$ is continuous on $[0,3]$.

No, because IVT requires opposite signs at the endpoints.

No, because $h(0)$ and $h(3)$ are both positive.

Explanation

This problem evaluates understanding of the Intermediate Value Theorem (IVT), ensuring a continuous function hits every value between its endpoints on a closed interval. With h continuous on [0,3], h(0) = 5, and h(3) = 9, the values go from 5 to 9. Therefore, 7 is between 5 and 9, so IVT promises a c in [0,3] with h(c) = 7. This applies even if both endpoints are positive, as long as the target is in between. A distractor might wrongly insist on opposite signs, but IVT isn't limited to roots; it's for any intermediate value. Use this checklist for IVT: ensure closed-interval continuity and that k is between f(a) and f(b).

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