4.7 Graph Linear Functions
Algebra I 4.7 Graph Linear Functions
EXAMPLE 1 f (x) 3x – 15 = (– 3) 3(– 3) – 15 f = = 24 ANSWER
(– 3) 3(– 3) – 15 f = 24 ANSWER The correct answer is A. A B C D
GUIDED PRACTICE 1. Evaluate the function h(x) = – 7x when x = 7. h(7) = – 49 2. For the function f(x) 2x – 10, find the value of x so that = = f(x) = 2x – 10 f(x) x – 10 = 8 x =
EXAMPLE 3 The gray wolf population in central Idaho was monitored over several years for a project aimed at boosting the number of wolves. The number of wolves can be modeled by the function f(x) = 37x + 7 where x is the number of years since 1995. Graph the function and identify its domain and range. GRAY WOLF
Graph a function EXAMPLE 3 To graph the function, make a table. x f(x) 37(0) + 7 = 7 1 37(1) + 7 = 44 2 37(2) + 7 = 81 The domain of the function is x From the graph or table, you can see that the range of the function is f(x) > =
2. WOLF POPULATION Use the model from Example 3 to find the value of x so that f(x) = 155. Explain what the solution means in this situation. SOLUTION x f(x) 37(0) + 7 = 7 1 37(1) + 7 = 44 2 37(2) + 7 = 81 3 37(3) + 7 = 118 4 37(4) + 7 = 155 4 years after 1995, the wolf population will be 155.
Graph the function. Compare the graph with the graph of f (x) x. =
EXAMPLE 4 Graph the function. Compare the graph with the graph of f (x) x. = a. g(x) = x + 3 b. h(x) = 2x Because the slope of the graph of h is greater than the slope of the graph of f, the graph of h rises faster from left to right. The y-intercept for both graphs is 0, so both lines pass through the origin. Because the graphs of g and f have the same slope, m = 1, the lines are parallel. Also, the y- intercept of the graph of g is 3 more than the y-intercept of the graph of f.
GUIDED PRACTICE Graph h(x) = – 3x. Compare the graph with the graph of f (x) = x. 3. Since the slope of the graph of h is negative the graph of h falls from left to right. The y-intercept for both graphs is 0, so both lines pass through the origin.
EXAMPLE 5 CABLE A cable company charges new customers $40 for installation and $60 per month for its service. The cost to the customer is given by the function f(x) = 60x +40 where x is the number of months of service. To attract new customers, the cable company reduces the installation fee to $5. A function for the cost with the reduced installation fee is g(x) = 60x + 5. Graph both functions. How is the graph of g related to the graph of f ?
EXAMPLE 5 The graphs of both functions are shown.
Both functions have a slope of 60, so they are parallel. The y-intercept of the graph of g is 35 less than the graph of f. So, the graph of g is a vertical translation of the graph of f.
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