Math Problem Statement

. Refer to the function g(x) = 7x + 2. (a) What are the domain and range of g? (b) Let h(x) = x2 + x + 1. Find an algebraic expression for g(h(x)). (c) Again using h(x) = x2 + x + 1, find an algebraic expression for 3g(x) − h(x). (d) Find a function equation for the inverse function, g−1. (e) What are the domain and range of g−1? 2. Refer to the graph of R(x) in Figure 3.2. The diagonal line y = x is included on the graph for reference. Note that the graph of R(x) includes the points (−7.5, 0), (−1, 2), (0, 4.5), and (6, 6). (a) What are the domain and range of R? (b) Draw the graph of the inverse function, R−1. (c) What are the domain and range of R−1? Figure 3.2: Graph of R(x) x 0 1 2 3 f (x) 3 0 2 -4 Table 3.14: f (x) 3. Refer to f in Table 3.14. (a) What are the domain and range of f ? (b) Find a function table for the inverse function, f −1. (c) What are the domain and range of f −1?

Solution

1. Refer to the function g(x)=7x+2g(x) = 7x + 2:

(a) Domain and Range of gg

  • Domain: g(x)=7x+2g(x) = 7x + 2 is a linear function, which is defined for all real numbers. Thus, the domain is (,)(-\infty, \infty).
  • Range: Since g(x)g(x) is linear and covers all real numbers, its range is also (,)(-\infty, \infty).

(b) Algebraic Expression for g(h(x))g(h(x))

Given h(x)=x2+x+1h(x) = x^2 + x + 1, substitute h(x)h(x) into g(x)g(x): g(h(x))=7h(x)+2=7(x2+x+1)+2=7x2+7x+7+2=7x2+7x+9g(h(x)) = 7h(x) + 2 = 7(x^2 + x + 1) + 2 = 7x^2 + 7x + 7 + 2 = 7x^2 + 7x + 9

(c) Algebraic Expression for 3g(x)h(x)3g(x) - h(x)

Substitute g(x)=7x+2g(x) = 7x + 2 and h(x)=x2+x+1h(x) = x^2 + x + 1: 3g(x)h(x)=3(7x+2)(x2+x+1)=21x+6x2x1=x2+20x+53g(x) - h(x) = 3(7x + 2) - (x^2 + x + 1) = 21x + 6 - x^2 - x - 1 = -x^2 + 20x + 5

(d) Function Equation for the Inverse, g1(x)g^{-1}(x)

To find the inverse, solve y=7x+2y = 7x + 2 for xx: y=7x+2    x=y27y = 7x + 2 \implies x = \frac{y - 2}{7} Thus, the inverse function is: g1(x)=x27g^{-1}(x) = \frac{x - 2}{7}

(e) Domain and Range of g1g^{-1}

  • Domain: Since g1(x)=x27g^{-1}(x) = \frac{x - 2}{7} is defined for all xx, its domain is (,)(-\infty, \infty).
  • Range: The output of g1(x)g^{-1}(x) is also all real numbers, so the range is (,)(-\infty, \infty).

2. Refer to the graph of R(x)R(x):

(a) Domain and Range of RR

From the given points (7.5,0),(1,2),(0,4.5),(6,6)(-7.5, 0), (-1, 2), (0, 4.5), (6, 6):

  • Domain: The set of xx-values is {7.5,1,0,6}\{-7.5, -1, 0, 6\}.
  • Range: The set of yy-values is {0,2,4.5,6}\{0, 2, 4.5, 6\}.

(b) Graph of the Inverse, R1R^{-1}

To graph R1R^{-1}, reflect each point of R(x)R(x) over the line y=xy = x. The new points are: R1={(0,7.5),(2,1),(4.5,0),(6,6)}R^{-1} = \{(0, -7.5), (2, -1), (4.5, 0), (6, 6)\}

(c) Domain and Range of R1R^{-1}

  • Domain: The set of xx-values of R1R^{-1} (which is the range of RR) is {0,2,4.5,6}\{0, 2, 4.5, 6\}.
  • Range: The set of yy-values of R1R^{-1} (which is the domain of RR) is {7.5,1,0,6}\{-7.5, -1, 0, 6\}.

3. Refer to ff in Table 3.14:

xxf(x)f(x)
03
10
22
3-4

(a) Domain and Range of ff

  • Domain: The set of xx-values is {0,1,2,3}\{0, 1, 2, 3\}.
  • Range: The set of yy-values is {3,0,2,4}\{3, 0, 2, -4\}.

(b) Function Table for f1f^{-1}

The inverse function swaps the xx- and yy-values of ff:

xxf1(x)f^{-1}(x)
30
01
22
-43

(c) Domain and Range of f1f^{-1}

  • Domain: The set of xx-values of f1f^{-1} (which is the range of ff) is {3,0,2,4}\{3, 0, 2, -4\}.
  • Range: The set of yy-values of f1f^{-1} (which is the domain of ff) is {0,1,2,3}\{0, 1, 2, 3\}.

Additional Questions:

  1. How does the graph of g(x)g(x) relate to its inverse g1(x)g^{-1}(x)?
  2. What happens if you compose gg with g1g^{-1}?
  3. Can you generalize the inverse formula for any linear function ax+bax + b?
  4. How do the properties of the graph R(x)R(x) change when reflected over y=xy = x?
  5. What insights can be drawn by analyzing f(x)f(x) and f1(x)f^{-1}(x) in terms of their domains and ranges?

Tip:

For any function ff, its inverse f1f^{-1} exists if and only if ff is one-to-one (passes the horizontal line test).

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Math Problem Analysis

Mathematical Concepts

Linear Functions
Inverse Functions
Quadratic Equations
Graphing
Domain and Range

Formulas

Linear function: g(x) = ax + b
Inverse function: g−1(x) = (x - b) / a
Quadratic function: h(x) = x^2 + x + c
Composition: f(g(x))
Reflection for inverses over y = x

Theorems

Horizontal Line Test for One-to-One Functions
Properties of Inverse Functions

Suitable Grade Level

Grades 10-12