Cogito
Calculus · Chapter 2 · Lesson 3
The Intermediate Value Theorem
A continuous graph cannot skip a value.
12 problems · about 21 minutes · FUN-1.A
Figure — use these to answer the problems
Warm Up
Straightforward practice. Get the method working first.
5 problemsf(1) = −3 and f(4) = 6. Does the theorem guarantee a root between them? 1 or 0.
AnswerWhy does the theorem require continuity?
- A jump lets the function step over the value entirely.
- Because the graph must be smooth.
f(x) = x² − 2. What is f(1)?
AnswerSame function. What is f(2)?
AnswerDoes the theorem guarantee a root between 1 and 2 there? 1 for yes, 0 for no.
Answer
Build It Up
The same ideas with more to keep track of.
3 problemsf(a) = 3 and f(b) = 9, both positive. Does the theorem guarantee a root? 1 or 0.
Answerf(a) = −4 and f(b) = 4. Does it guarantee a root? 1 or 0.
AnswerDoes the theorem tell you how many roots there are? 1 for yes, 0 for no.
Answer
Stretch Yourself
Mixed problems. Work out what kind of question it is before you start.
4 problemsPut the argument in order.
Write 1 to 4 in the boxes to put these in order.
- Confirm the function is continuous on the closed interval.
- Evaluate the function at both endpoints.
- Check that the target value lies between them.
- Conclude the value is attained somewhere inside.
f(x) = x³. What is f(−2)?
AnswerThe Endpoints
f(x) = x³ − x − 1. What is f(1)?
AnswerThe Other End
Same function. What is f(2)?
Answer