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This lesson focuses on transforming polynomial functions through various operations, including vertical/horizontal translations, reflections across axes, and compressions or stretches. Using examples like f(x) = x³ - 6 and transformations such as g(x) = f(x) - 2 or g(x) = -f(x), students will explore how to graph these transformations and understand their effects on the polynomial's shape. Problem sets are provided for guided practice, reinforcing the learning objectives and preparing students for further topics, such as exponential functions.
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Chapter 3 3-8 transforming polynomial functions
SAT Problem of the day • Lines l and m are perpendicular lines that intersect at the origin. If line l passes through the point (2,-1), then line m must pass through which of the following points? • A) (0,2) • B)(1,3) • C)(2,1) • D)(3,6) • E)(4,0)
solution • Right Answer: D
Objectives • Transform polynomial functions.
Transforming polynomial functions • You can perform the same transformations on polynomial functions that you performed on quadratic and linear functions.
Example#1 • Translating polynomial • For f(x) = x3 – 6, write the rule for each function and sketch its graph. • g(x) = f(x) –2 • Solution: • To graph g(x) = f(x) – 2, translate the graph of f(x) 2 units down. • This is a vertical translation.
Example#2 • For f(x) = x3 – 6, write the rule for each function and sketch its graph. • h(x) = f(x + 3) • Solution: • To graph h(x) = f(x + 3), translate the graph 3 units to the left. • This is a horizontal translation.
Example#3 • For f(x) = x3 + 4, write the rule for each function and sketch its graph. • g(x) = f(x) –5 • Solution: • To graph g(x) = f(x) – 5, translate the graph of f(x) 5 units down. • This is a vertical translation.
Student guided practice • Do problems 1 and 4 in your book page 207
Reflecting polynomial functions Example#4 • Let f(x) = x3 + 5x2 – 8x + 1. Write a function g that performs each transformation. • Reflect f(x) across the x-axis. • Solution : • g(x) = –f(x) • g(x) = –(x3 + 5x2 – 8x + 1) • g(x) = –x3 – 5x2 + 8x – 1
Example#5 • Let f(x) = x3 + 5x2 – 8x + 1. Write a function g that performs each transformation. • Reflect f(x) across the y-axis. • Solution: • g(x) = f(–x) • g(x) = (–x)3 + 5(–x)2 – 8(–x) + 1 • g(x) = –x3 + 5x2 + 8x + 1
Student guided practice Do problems 5 and 6 in your book page 207
Do compressions/stretches • Let f(x) = 2x4 – 6x2 + 1. Graph f and g on the same coordinate plane. Describe g as a transformation of f. • Solution: • g(x) = 1/2f(x) • g(x) = 1/2 (2x4 – 6x2 + 1) • g(x) = x4 – 3x2+ 1/2 • g(x) is a vertical compression of f(x).
Example • Let f(x) = 2x4 – 6x2 + 1. Graph f and g on the same coordinate plane. Describe g as a transformation of f. • g(x) = f( 1/3 x) • Solution: • g(x) = 2( 1/3x)4– 6(1/3x)2+ 1 • g(x) = 2/81x4– 2/3 x2+ 1 • g(x) is a horizontal stretch of f(x).
Student guided practice • Do problems 7-9
Combining transformations • Write a function that transforms f(x) = 6x3 – 3 in each of the following ways. Support your solution by using a graphing calculator. • Compress vertically by a factor of 1/3 , and shift 2 units right. • Solution: • g(x) = 1/3f(x – 2) • g(x) = 1/3(6(x – 2)3 – 3) • g(x) = 2(x – 2)3 – 1
Write a function that transforms f(x) = 6x3 – 3 in each of the following ways. Support your solution by using a graphing calculator. • Reflect across the y-axis and shift 2 units down. • Solution: • g(x) = f(–x)– 2 • g(x) = (6(–x)3– 3) – 2 • g(x) = –6x3 – 5
Student guided practice • Do problems 10-12 pg. 207
Homework!! • Do problems 14-20 page 207 and 208 in your book
Closure • Today we learn about transforming polynomial • Next class we are going to learn about Exponential functions , growth, and decay