Math Problem Statement

Suppose that  f  is continuous on [0, 6] and that the only solutions of the equation  f (x) = 3 are x = 1 and x = 5. If  f (4) = 5, then which of the following statements must be true?

(i)  f (2)  >  3 (ii)  f (0)  <  3 (iii)  f (6)  <  3

Solution

We are given that ff is continuous on the interval [0,6][0, 6] and that the only solutions to the equation f(x)=3f(x) = 3 occur at x=1x = 1 and x=5x = 5. This implies that between x=1x = 1 and x=5x = 5, the function f(x)f(x) does not equal 3 anywhere else. Additionally, we know that f(4)=5f(4) = 5, which is greater than 3.

We will now analyze each of the three statements:

Statement (i): f(2)>3f(2) > 3

  • The function is continuous, and the only points where f(x)=3f(x) = 3 are x=1x = 1 and x=5x = 5.
  • From the Intermediate Value Theorem (IVT), since f(1)=3f(1) = 3 and f(4)=5f(4) = 5, f(x)f(x) must be greater than 3 between x=1x = 1 and x=4x = 4. Hence, f(2)>3f(2) > 3.

So, statement (i) is true.

Statement (ii): f(0)<3f(0) < 3

  • Since f(x)=3f(x) = 3 only at x=1x = 1, and f(x)f(x) must be either greater than or less than 3 outside the point x=1x = 1.
  • If f(0)3f(0) \geq 3, the continuity of ff would force the function to reach 3 before x=1x = 1, violating the condition that f(x)=3f(x) = 3 only at x=1x = 1.
  • Therefore, f(0)f(0) must be less than 3 to avoid crossing 3 anywhere between x=0x = 0 and x=1x = 1.

So, statement (ii) is true.

Statement (iii): f(6)<3f(6) < 3

  • Similarly, f(x)=3f(x) = 3 only at x=5x = 5, and for f(x)f(x) to stay above or at 3 after x=5x = 5, it would have to cross 3 again after x=5x = 5, which would contradict the given condition.
  • Therefore, f(6)f(6) must be less than 3 to ensure that the function does not cross the value 3 after x=5x = 5.

So, statement (iii) is true.

Conclusion:

All three statements must be true. Therefore, the correct answer is that statements (i), (ii), and (iii) are all true.


Do you want more details or have any questions? Here are some additional questions to explore:

  1. Can the Intermediate Value Theorem be applied to any function that is not continuous?
  2. What happens if f(2)=3f(2) = 3? Would this affect the results?
  3. How would the situation change if f(x)=3f(x) = 3 had more solutions on [0,6][0, 6]?
  4. Could there be another point where f(x)=5f(x) = 5 apart from x=4x = 4?
  5. What would happen if f(x)f(x) was discontinuous at any point in the interval?

Tip: The Intermediate Value Theorem is a powerful tool when analyzing continuous functions, as it guarantees that a function takes on all values between any two points on its graph.

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Math Problem Analysis

Mathematical Concepts

Continuity
Intermediate Value Theorem
Function Analysis

Formulas

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Theorems

Intermediate Value Theorem

Suitable Grade Level

Grades 10-12