<< Chapter < Page Chapter >> Page >

Using the intermediate value theorem

Show that the function f ( x ) = x 3 5 x 2 + 3 x + 6 has at least two real zeros between x = 1 and x = 4.

As a start, evaluate f ( x ) at the integer values x = 1 , 2 , 3 , and 4. See [link] .

x 1 2 3 4
f ( x ) 5 0 –3 2

We see that one zero occurs at x = 2. Also, since f ( 3 ) is negative and f ( 4 ) is positive, by the Intermediate Value Theorem, there must be at least one real zero between 3 and 4.

We have shown that there are at least two real zeros between x = 1 and x = 4.

Got questions? Get instant answers now!
Got questions? Get instant answers now!

Show that the function f ( x ) = 7 x 5 9 x 4 x 2 has at least one real zero between x = 1 and x = 2.

Because f is a polynomial function and since f ( 1 ) is negative and f ( 2 ) is positive, there is at least one real zero between x = 1 and x = 2.

Got questions? Get instant answers now!

Writing formulas for polynomial functions

Now that we know how to find zeros of polynomial functions, we can use them to write formulas based on graphs. Because a polynomial function    written in factored form will have an x -intercept where each factor is equal to zero, we can form a function that will pass through a set of x -intercepts by introducing a corresponding set of factors.

Factored form of polynomials

If a polynomial of lowest degree p has horizontal intercepts at x = x 1 , x 2 , , x n , then the polynomial can be written in the factored form: f ( x ) = a ( x x 1 ) p 1 ( x x 2 ) p 2 ( x x n ) p n where the powers p i on each factor can be determined by the behavior of the graph at the corresponding intercept, and the stretch factor a can be determined given a value of the function other than the x -intercept.

Given a graph of a polynomial function, write a formula for the function.

  1. Identify the x -intercepts of the graph to find the factors of the polynomial.
  2. Examine the behavior of the graph at the x -intercepts to determine the multiplicity of each factor.
  3. Find the polynomial of least degree containing all the factors found in the previous step.
  4. Use any other point on the graph (the y -intercept may be easiest) to determine the stretch factor.

Writing a formula for a polynomial function from the graph

Write a formula for the polynomial function shown in [link] .

Graph of a positive even-degree polynomial with zeros at x=-3, 2, 5 and y=-2.

This graph has three x -intercepts: x = −3 , 2 , and 5. The y -intercept is located at ( 0 , 2 ) . At x = −3 and x = 5 , the graph passes through the axis linearly, suggesting the corresponding factors of the polynomial will be linear. At x = 2 , the graph bounces at the intercept, suggesting the corresponding factor of the polynomial will be second degree (quadratic). Together, this gives us

f ( x ) = a ( x + 3 ) ( x 2 ) 2 ( x 5 )

To determine the stretch factor, we utilize another point on the graph. We will use the y - intercept ( 0 , 2 ) , to solve for a .

f ( 0 ) = a ( 0 + 3 ) ( 0 2 ) 2 ( 0 5 ) −2 = a ( 0 + 3 ) ( 0 2 ) 2 ( 0 5 ) −2 = 60 a a = 1 30

The graphed polynomial appears to represent the function f ( x ) = 1 30 ( x + 3 ) ( x 2 ) 2 ( x 5 ) .

Got questions? Get instant answers now!
Got questions? Get instant answers now!

Given the graph shown in [link] , write a formula for the function shown.

Graph of a negative even-degree polynomial with zeros at x=-1, 2, 4 and y=-4.

f ( x ) = 1 8 ( x 2 ) 3 ( x + 1 ) 2 ( x 4 )

Got questions? Get instant answers now!

Using local and global extrema

With quadratics, we were able to algebraically find the maximum or minimum value of the function by finding the vertex. For general polynomials, finding these turning points is not possible without more advanced techniques from calculus. Even then, finding where extrema occur can still be algebraically challenging. For now, we will estimate the locations of turning points using technology to generate a graph.

Questions & Answers

what does preconceived mean
sammie Reply
physiological Psychology
Nwosu Reply
How can I develope my cognitive domain
Amanyire Reply
why is communication effective
Dakolo Reply
Communication is effective because it allows individuals to share ideas, thoughts, and information with others.
effective communication can lead to improved outcomes in various settings, including personal relationships, business environments, and educational settings. By communicating effectively, individuals can negotiate effectively, solve problems collaboratively, and work towards common goals.
it starts up serve and return practice/assessments.it helps find voice talking therapy also assessments through relaxed conversation.
miss
Every time someone flushes a toilet in the apartment building, the person begins to jumb back automatically after hearing the flush, before the water temperature changes. Identify the types of learning, if it is classical conditioning identify the NS, UCS, CS and CR. If it is operant conditioning, identify the type of consequence positive reinforcement, negative reinforcement or punishment
Wekolamo Reply
please i need answer
Wekolamo
because it helps many people around the world to understand how to interact with other people and understand them well, for example at work (job).
Manix Reply
Agreed 👍 There are many parts of our brains and behaviors, we really need to get to know. Blessings for everyone and happy Sunday!
ARC
A child is a member of community not society elucidate ?
JESSY Reply
Isn't practices worldwide, be it psychology, be it science. isn't much just a false belief of control over something the mind cannot truly comprehend?
Simon Reply
compare and contrast skinner's perspective on personality development on freud
namakula Reply
Skinner skipped the whole unconscious phenomenon and rather emphasized on classical conditioning
war
explain how nature and nurture affect the development and later the productivity of an individual.
Amesalu Reply
nature is an hereditary factor while nurture is an environmental factor which constitute an individual personality. so if an individual's parent has a deviant behavior and was also brought up in an deviant environment, observation of the behavior and the inborn trait we make the individual deviant.
Samuel
I am taking this course because I am hoping that I could somehow learn more about my chosen field of interest and due to the fact that being a PsyD really ignites my passion as an individual the more I hope to learn about developing and literally explore the complexity of my critical thinking skills
Zyryn Reply
good👍
Jonathan
and having a good philosophy of the world is like a sandwich and a peanut butter 👍
Jonathan
generally amnesi how long yrs memory loss
Kelu Reply
interpersonal relationships
Abdulfatai Reply
What would be the best educational aid(s) for gifted kids/savants?
Heidi Reply
treat them normal, if they want help then give them. that will make everyone happy
Saurabh
What are the treatment for autism?
Magret Reply
hello. autism is a umbrella term. autistic kids have different disorder overlapping. for example. a kid may show symptoms of ADHD and also learning disabilities. before treatment please make sure the kid doesn't have physical disabilities like hearing..vision..speech problem. sometimes these
Jharna
continue.. sometimes due to these physical problems..the diagnosis may be misdiagnosed. treatment for autism. well it depends on the severity. since autistic kids have problems in communicating and adopting to the environment.. it's best to expose the child in situations where the child
Jharna
child interact with other kids under doc supervision. play therapy. speech therapy. Engaging in different activities that activate most parts of the brain.. like drawing..painting. matching color board game. string and beads game. the more you interact with the child the more effective
Jharna
results you'll get.. please consult a therapist to know what suits best on your child. and last as a parent. I know sometimes it's overwhelming to guide a special kid. but trust the process and be strong and patient as a parent.
Jharna
Got questions? Join the online conversation and get instant answers!
Jobilize.com Reply
Practice Key Terms 4

Get Jobilize Job Search Mobile App in your pocket Now!

Get it on Google Play Download on the App Store Now




Source:  OpenStax, Algebra and trigonometry. OpenStax CNX. Nov 14, 2016 Download for free at https://legacy.cnx.org/content/col11758/1.6
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Algebra and trigonometry' conversation and receive update notifications?

Ask