Example 1 Estimate Function Values A. ADVERTISING The function f (x) = –5x x approximates the profit at a toy company, where x represents marketing costs and f (x) represents profit. Both costs and profits are measured in tens of thousands of dollars. Use the graph to estimate the profit when marketing costs are $30,000. Confirm your estimate algebraically.

Example 1 Answer: $1,050,000 Estimate Function Values $30,000 is three ten thousands. The function value at x = 3 appears to be about 100 ten thousands, so the total profit was about $1,000,000. To confirm this estimate algebraically, find f(3). f(3) =  5(3) (3) = 105, or about $1,050,000. The graphical estimate of about $1,000,000 is reasonable.

Example 1 Estimate Function Values B. ADVERTISING The function f (x) = –5x x approximates the profit at a toy company, where x represents marketing costs and f (x) represents profit. Both costs and profits are measured in tens of thousands of dollars. Use the graph to estimate marketing costs when the profit is $1,250,000. Confirm your estimate algebraically.

Example 1 Answer: $50,000 Estimate Function Values $1,250,000 is 125 ten thousands. The value of the function appears to reach 125 ten thousands for an x-value of about 5. This represents an estimate of 5 ● $10,000 or $50,000. To confirm algebraically, find f(5). f(5) =  5(5) (5) = 125, or about $1,250,000. The graphical estimate that marketing costs are $50,000 when the profit is $1,250,000 is reasonable.

Example 2 Find Domain and Range Use the graph of f to find the domain and range of the function.

Example 2 Find Domain and Range Domain The dot at (3,  3) indicates that the domain of f ends at 3 and includes 3. The arrow on the left side indicates that the graph will continue without bound. The domain of f is. In set-builder notation, the domain is. Range The graph does not extend above y = 2, but f (x) decreases without bound for smaller and smaller values of x. So the range of f is.

Example 2 Find Domain and Range Answer: D: R:

Example 2 Use the graph of f to find the domain and range of the function. A.Domain: Range: B.Domain: Range: C.Domain: Range: D.Domain: Range:

Example 3 Find y-Intercepts A. Use the graph of the function f (x) = x 2 – 4x + 4 to approximate its y-intercept. Then find the y-intercept algebraically.

Example 3 Find y-Intercepts Answer: 4 Estimate Graphically It appears that f (x) intersects the y-axis at approximately (0, 4), so the y-intercept is about 4. Solve Algebraically Find f (0). f (0) = (0) 2 – 4(0) + 4 = 4. The y-intercept is 4.

Example 3 Find y-Intercepts B. Use the graph of the function g (x) =│x + 2│– 3 to approximate its y-intercept. Then find the y-intercept algebraically.

Example 3 Find y-Intercepts Answer:  1 Estimate Graphically g (x) intersects the y-axis at approximately (0,  1), so the y-intercept is about  1. Solve Algebraically Find g (0). g (0) = |0 + 2| – 3 or –1 The y-intercept is –1.

Example 4 Find Zeros Use the graph of f (x) = x 3 – x to approximate its zero(s). Then find its zero(s) algebraically.

Example 4 Answer:  1, 0, 1 Find Zeros Estimate Graphically The x-intercepts appear to be at about  1, 0, and 1. Solve Algebraically x 3 – x= 0Let f (x) = 0. x(x 2 – 1)= 0Factor. x(x – 1)(x + 1)= 0Factor. x = 0 orx – 1= 0 or x + 1= 0Zero Product Property x = 0x= 1 x=  1Solve for x. The zeros of f are 0, 1, and  1.

Example 4 A.–2.5 B.–1 C.5 D.9 Use the graph of to approximate its zero(s). Then find its zero(s) algebraically.

Key Concept 1

Example 5 Test for Symmetry A. Use the graph of the equation y = x to test for symmetry with respect to the x-axis, the y-axis, and the origin. Support the answer numerically. Then confirm algebraically.

Example 5 Test for Symmetry Analyze Graphically The graph appears to be symmetric with respect to the y-axis because for every point (x, y) on the graph, there is a point (  x, y). Support Numerically A table of values supports this conjecture.

Example 5 Answer:symmetric with respect to the y-axis Test for Symmetry Confirm Algebraically Because x is equivalent to (  x) 2 + 2, the graph is symmetric with respect to the y-axis.

Example 5 Test for Symmetry B. Use the graph of the equation xy = –6 to test for symmetry with respect to the x-axis, the y-axis, and the origin. Support the answer numerically. Then confirm algebraically.

Example 5 Test for Symmetry Analyze Graphically The graph appears to be symmetric with respect to the origin because for every point (x, y) on the graph, there is a point (  x,  y). Support Numerically A table of values supports this conjecture.

Example 5 Answer:symmetric with respect to the origin Test for Symmetry Confirm Algebraically Because (  x)(  y) =  6 is equivalent to (x)(y) =  6, the graph is symmetric with respect to the origin.

Key Concept 2

Example 6 A. Graph the function f (x) = x 2 – 4x + 4 using a graphing calculator. Analyze the graph to determine whether the function is even, odd, or neither. Confirm algebraically. If even or odd, describe the symmetry of the graph of the function. Identify Even and Odd Functions

Example 6 Answer: neither Identify Even and Odd Functions It appears that the graph of the function is neither symmetric with respect to the y-axis nor to the origin. Test this conjecture algebraically. f (  x)= (  x) 2 – 4(  x) + 4 Substitute  x for x. = x 2 + 4x + 4Simplify. Since –f (x) =  x 2 + 4x  4, the function is neither even nor odd because f (  x) ≠ f (x) or –f (x).

Example 6 B. Graph the function f (x) = x 2 – 4 using a graphing calculator. Analyze the graph to determine whether the function is even, odd, or neither. Confirm algebraically. If even or odd, describe the symmetry of the graph of the function. Identify Even and Odd Functions

Example 6 Answer: even; symmetric with respect to the y-axis Identify Even and Odd Functions From the graph, it appears that the function is symmetric with respect to the y-axis. Test this conjecture algebraically. f (  x)= (  x) 2 – 4 Substitute  x for x. = x 2  4 Simplify. = f (x) Original function f (x) = x 2 – 4 The function is even because f (  x) = f (x).

Example 6 C. Graph the function f (x) = x 3 – 3x 2 – x + 3 using a graphing calculator. Analyze the graph to determine whether the function is even, odd, or neither. Confirm algebraically. If even or odd, describe the symmetry of the graph of the function. Identify Even and Odd Functions

Example 6 Answer: neither Identify Even and Odd Functions From the graph, it appears that the function is neither symmetric with respect to the y-axis nor to the origin. Test this conjecture algebraically. f (–x)= (–x) 3 – 3(–x) 2 – (–x) + 3 Substitute –x for x. = –x 3 – 3x 2 + x + 3 Simplify. Because –f (x) = –x 3 + 3x 2 + x – 3, the function is neither even nor odd because f (–x) ≠ f (x) or –f (x).