Combinations of Functions; Composite Functions
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Combinations of Functions; Composite Functions. Objectives. Students will be able to add, subtract, multiply and divide functions. Students will be able to find the composition of one function with another function.
Combinations of Functions; Composite Functions
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Objectives • Students will be able to add, subtract, multiply and divide functions. • Students will be able to find the composition of one function with another function. • Students will be able to use combinations and composition of functions to model and solve real life problems.
Let f and g be two functions. The sum of f + g, the differencef – g, the productfg, and the quotientf /g are functions whose domains are the set of all real numbers common to the domains of f and g, defined as follows: Sum: (f + g)(x) = f (x)+g(x) Difference: (f – g)(x) = f (x) – g(x) Product: (f • g)(x) = f (x) • g(x) Quotient: (f / g)(x) = f (x)/g(x), provided g(x) does not equal 0 Definitions: Sum, Difference, Product, and Quotient of Functions
Let f(x) = 2x+1 and g(x) = x2-2. Find f + g, f - g, fg, and f/g and state the domain of each.. Solution: f+g = 2x+1 + x2-2 = x2+2x-1 f-g = (2x+1) - (x2-2)= -x2+2x+3 fg = (2x+1)(x2-2) = 2x3+x2-4x-2 f/g = (2x+1)/(x2-2) (f+g)(2) = (2)2+2(2)-1 = 7 Example
The composition of the function f with g is denoted by fog and is defined by the equation (fog)(x) = f (g(x)). The domain of the composite function fog is the set of all x such that x is in the domain of g and g(x) is in the domain of f. See pg. 105 figure P.96 The Composition of Functions
Given f (x) = 2x – 8 and g(x) = x2 - 5, find: a.(fog)(x) b. (gof)(x) What is the domain of each? Try Page 107 # 12, 16, 26, 28, 38, 42 Homework: Page 107 – 108 #9, 13, 15, 17, 21, 25, 27, 37 – 47 0dd Example