Quadratic Equations and Applications

Lesson 9

Math

Unit 8

9th Grade

Lesson 9 of 15

Objective


Describe transformations to quadratic functions. Write equations for transformed quadratic functions.

Common Core Standards


Core Standards

  • F.BF.B.3 — Identify the effect on the graph of replacing f(x) by f(x) + k, k f(x), f(kx), and f(x + k) for specific values of k (both positive and negative); find the value of k given the graphs. Experiment with cases and illustrate an explanation of the effects on the graph using technology. Include recognizing even and odd functions from their graphs and algebraic expressions for them.

Foundational Standards

  • 8.G.A.2
  • 8.G.A.3

Criteria for Success


  1. Describe transformations to quadratic functions as seen in graphs and equations. 
  2. Identify transformations as they are presented in the equations of quadratic functions.
  3. Write equations to represent the transformation of quadratic graphs as seen in graphs and as described verbally.

Tips for Teachers


Prior to this lesson, it may be helpful to recall and review the transformations that students studied in Unit 5, introduced using the absolute value function.

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Anchor Problems

25-30 minutes


Problem 1

Suppose $${f(x)=x^2}$$, where $$x$$ can be any real number. 

Using a graphing calculator or other graphing technology, graph the function $$f$$ and each of the transformations to function $$f$$ shown below. For each graph, describe how the graph of each transformation compares to function $$f$$.

a.  $$a(x)=f(x)+2$$

b.  $$b(x)=-2f(x)$$

c.  $$c(x)={1\over2} f(x)$$

d.  $$d(x)=f(x+2)$$

e.  $$e(x)=-f(x-2)-2$$

Guiding Questions

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References

Illustrative Mathematics Building a quadratic function from f(x)=x^2

Building a quadratic function from f(x)=x^2, accessed on Aug. 18, 2017, 12:24 p.m., is licensed by Illustrative Mathematics under either the CC BY 4.0 or CC BY-NC-SA 4.0. For further information, contact Illustrative Mathematics.

Modified by Fishtank Learning, Inc.

Problem 2

Graphs of functions $${{{f(x)}}}$$  and $${{{{g(x)}} }}$$ are shown below. In each pair of graphs, the graph of function $${{{{g(x)}} }}$$ represents a transformation of function $${{{f(x)}}}$$.

  1. For each pair of graphs, describe the transformation that maps the graph of $${{{f(x)}}}$$ to the graph of $${{g(x)}}$$.
  2. Let $${{g(x)}}=a(x-h)^2+k$$. For each graph of $${{g(x)}}$$, identify the values of $$a$$, $$h$$, and $$k$$ to make the equation true. 

Guiding Questions

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Problem 3

A quadratic function $${{f(x)}}$$ is vertically stretched by a factor of $$3$$ and translated right by $$6$$ units.

Write an equation for $${h(x)}$$ to represent the transformation of the graph of function $${{f(x)}}$$ if

a.  $${{f(x)}}=x^2$$

b.  $${{f(x)}}=x^2-4$$

c.  $${{f(x)}}=-(x-1)^2+2 $$

Guiding Questions

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Problem Set

15-20 minutes


Give your students more opportunities to practice the skills in this lesson with a downloadable problem set aligned to the daily objective.

Target Task

5-10 minutes


Function $$f$$ is given by the equation $$f(x)=(x-2)^2+3$$.

Function $$g$$ is given by the equation $$g(x)=-(x+1)^2-1$$.

Describe the transformations that take the graph of $$f(x)$$ to the graph of $$g(x)$$.

Additional Practice


The following resources include problems and activities aligned to the objective of the lesson that can be used for additional practice or to create your own problem set.

Next

Graph and describe transformations to quadratic functions in mathematical and real-world situations.

Lesson 10
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Lesson Map

A7CB09C2-D12F-4F55-80DB-37298FF0A765

Topic A: Deriving the Quadratic Formula

Topic B: Transformations and Applications

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