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Page 1 chaPTer 7 FUNCTIONS AND GRAPHS 237 7 Functions and graphs In this chapter, you will: • use the point-by-point plotting method for sketching the graph of an equation in two variables • with this method, you construct a table of values that consists of several solution points of the equation and then plot the solution points on the Cartesian plane 2153 TechMaths Eng G10 LB.indb 237 2015/10/22 3:41 PM Page 2 chaPTer 7 FUNCTIONS AND GRAPHS 237 7 Functions and graphs In this chapter, you will: • use the point-by-point plotting method for sketching the graph of an equation in two variables • with this method, you construct a table of values that consists of several solution points of the equation and then plot the solution points on the Cartesian plane 2153 TechMaths Eng G10 LB.indb 237 2015/10/22 3:41 PM 238 Technical Ma TheMaTicS Grade 10 7.1 Function notation Function notation is one of many other conventions that we use to represent and name relationships between the values of two variables. The definition of a function consists of the following components: • the name of the function • the variable that represents a value to evaluate the function • a rule that says how to calculate the function's output for the given input value The number that results from applying the rule to a specific input value is called an output value and is represented by f (x). Consider the function given: f (x) = 3x + 2 3x + 2 is a rule that says how to calculate the function’s output for a given input x is the variable that represents a value at which to evaluate the function the letter f is the name of the function 7.2 revision of linear functions Work through the examples to revise what you have learned about linear functions. w orked examples A. Problem: (a) Copy and complete the table below for the functions defined by f (x) = x. f (-5) = -5 f (-4) = -4 f (-3) = -3 f (-2) = -2 f (-1) = -1 f (0) = 0 f (1) = 1 f (2) = 2 f (3) = 3 f (4) = 4 f (5) = 5 Solution: (a) x -5 -4 -3 -2 -1 0 1 2 3 4 5 f (x) -5 -4 -3 -2 -1 0 1 2 3 4 5 2153 TechMaths Eng G10 LB.indb 238 2015/10/22 3:41 PM Page 3 chaPTer 7 FUNCTIONS AND GRAPHS 237 7 Functions and graphs In this chapter, you will: • use the point-by-point plotting method for sketching the graph of an equation in two variables • with this method, you construct a table of values that consists of several solution points of the equation and then plot the solution points on the Cartesian plane 2153 TechMaths Eng G10 LB.indb 237 2015/10/22 3:41 PM 238 Technical Ma TheMaTicS Grade 10 7.1 Function notation Function notation is one of many other conventions that we use to represent and name relationships between the values of two variables. The definition of a function consists of the following components: • the name of the function • the variable that represents a value to evaluate the function • a rule that says how to calculate the function's output for the given input value The number that results from applying the rule to a specific input value is called an output value and is represented by f (x). Consider the function given: f (x) = 3x + 2 3x + 2 is a rule that says how to calculate the function’s output for a given input x is the variable that represents a value at which to evaluate the function the letter f is the name of the function 7.2 revision of linear functions Work through the examples to revise what you have learned about linear functions. w orked examples A. Problem: (a) Copy and complete the table below for the functions defined by f (x) = x. f (-5) = -5 f (-4) = -4 f (-3) = -3 f (-2) = -2 f (-1) = -1 f (0) = 0 f (1) = 1 f (2) = 2 f (3) = 3 f (4) = 4 f (5) = 5 Solution: (a) x -5 -4 -3 -2 -1 0 1 2 3 4 5 f (x) -5 -4 -3 -2 -1 0 1 2 3 4 5 2153 TechMaths Eng G10 LB.indb 238 2015/10/22 3:41 PM chaPTer 7 FUNCTIONS AND GRAPHS 239 (b) Draw the graph of the function by plotting the coordinates on the Cartesian plane. (c) The x-intercept: (0; 0) (d) The y-intercept: (0 0) (e) Domain: x ? R (f) Range: y ? R x y –14 –12 –10 –6 –4 –2 2 0 4 6 8 10 12 14 –8 10 8 6 4 –2 –4 –6 –8 –10 2 w orked example B. Problem: A graph of a certain function is given below. x y –6 –4 –2 2 0 4 6 8 –8 12 10 8 6 4 –2 –4 –6 –8 –10 2 Copy and complete the table for this function by reading the values from the graph. Solution: x -5 -4 -3 -2 -1 0 1 2 3 4 5 f (x) -8 -6 -4 -2 0 2 4 6 8 10 12 (x; f (x)) (-5; -8) (-4; -6) (-3; -4) (-2; -2) (-1; 0) (0; 2) (1; 4) (2; 6) (3; 8) (4; 10) (5; 12) (b) x-intercept: (-1; 0) (c) y-intercept: (0; 2) (d) Domain: x ? R (e) Range: y ? R The domain is the set of all possible input values to which the rule applies. The range is the set of all possible output values to which the rule applies. 2153 TechMaths Eng G10 LB.indb 239 2015/10/22 3:41 PM Page 4 chaPTer 7 FUNCTIONS AND GRAPHS 237 7 Functions and graphs In this chapter, you will: • use the point-by-point plotting method for sketching the graph of an equation in two variables • with this method, you construct a table of values that consists of several solution points of the equation and then plot the solution points on the Cartesian plane 2153 TechMaths Eng G10 LB.indb 237 2015/10/22 3:41 PM 238 Technical Ma TheMaTicS Grade 10 7.1 Function notation Function notation is one of many other conventions that we use to represent and name relationships between the values of two variables. The definition of a function consists of the following components: • the name of the function • the variable that represents a value to evaluate the function • a rule that says how to calculate the function's output for the given input value The number that results from applying the rule to a specific input value is called an output value and is represented by f (x). Consider the function given: f (x) = 3x + 2 3x + 2 is a rule that says how to calculate the function’s output for a given input x is the variable that represents a value at which to evaluate the function the letter f is the name of the function 7.2 revision of linear functions Work through the examples to revise what you have learned about linear functions. w orked examples A. Problem: (a) Copy and complete the table below for the functions defined by f (x) = x. f (-5) = -5 f (-4) = -4 f (-3) = -3 f (-2) = -2 f (-1) = -1 f (0) = 0 f (1) = 1 f (2) = 2 f (3) = 3 f (4) = 4 f (5) = 5 Solution: (a) x -5 -4 -3 -2 -1 0 1 2 3 4 5 f (x) -5 -4 -3 -2 -1 0 1 2 3 4 5 2153 TechMaths Eng G10 LB.indb 238 2015/10/22 3:41 PM chaPTer 7 FUNCTIONS AND GRAPHS 239 (b) Draw the graph of the function by plotting the coordinates on the Cartesian plane. (c) The x-intercept: (0; 0) (d) The y-intercept: (0 0) (e) Domain: x ? R (f) Range: y ? R x y –14 –12 –10 –6 –4 –2 2 0 4 6 8 10 12 14 –8 10 8 6 4 –2 –4 –6 –8 –10 2 w orked example B. Problem: A graph of a certain function is given below. x y –6 –4 –2 2 0 4 6 8 –8 12 10 8 6 4 –2 –4 –6 –8 –10 2 Copy and complete the table for this function by reading the values from the graph. Solution: x -5 -4 -3 -2 -1 0 1 2 3 4 5 f (x) -8 -6 -4 -2 0 2 4 6 8 10 12 (x; f (x)) (-5; -8) (-4; -6) (-3; -4) (-2; -2) (-1; 0) (0; 2) (1; 4) (2; 6) (3; 8) (4; 10) (5; 12) (b) x-intercept: (-1; 0) (c) y-intercept: (0; 2) (d) Domain: x ? R (e) Range: y ? R The domain is the set of all possible input values to which the rule applies. The range is the set of all possible output values to which the rule applies. 2153 TechMaths Eng G10 LB.indb 239 2015/10/22 3:41 PM 240 Technical Ma TheMaTicS Grade 10 exercises 1 Copy and complete the table for the functions defined by: (a) f (x) = -x (b) g (x) = x + 5 (c) h (x) = -x - 1 x -5 -4 -3 -2 -1 0 1 2 3 4 5 6 f (x) g (x) h (x) 2 Draw the graphs of each function in exercise 1 above on the same set of axes. 3 Complete the table below for the three functions drawn in exercise 2. Function x-intercept y-intercept Domain r ange f (x) = -x g (x) = x + 5 h (x) = -x - 1 4 Use the intercept method to sketch the graphs of the following functions: (a) y = x + 2 (b) y = x - 3 (c) y = 2x + 1 (d) y = -2x + 4 (e) x = y - 4 (f) x = y (g) y = -3x + 6 5 A graph of a certain function g (x) is given below. Copy the table below for the function g (x). By reading of corresponding x- and y-values of points on the graph of g (x), complete the table by writing down specific corresponding x- and y-values. x y –5 –6 –3 –2 –1 1 0 2 3 4 5 6 7 –4 6 7 5 4 3 2 –1 –2 –3 –4 –5 –6 –7 1 x y = g (x) 2153 TechMaths Eng G10 LB.indb 240 2015/10/22 3:41 PM Page 5 chaPTer 7 FUNCTIONS AND GRAPHS 237 7 Functions and graphs In this chapter, you will: • use the point-by-point plotting method for sketching the graph of an equation in two variables • with this method, you construct a table of values that consists of several solution points of the equation and then plot the solution points on the Cartesian plane 2153 TechMaths Eng G10 LB.indb 237 2015/10/22 3:41 PM 238 Technical Ma TheMaTicS Grade 10 7.1 Function notation Function notation is one of many other conventions that we use to represent and name relationships between the values of two variables. The definition of a function consists of the following components: • the name of the function • the variable that represents a value to evaluate the function • a rule that says how to calculate the function's output for the given input value The number that results from applying the rule to a specific input value is called an output value and is represented by f (x). Consider the function given: f (x) = 3x + 2 3x + 2 is a rule that says how to calculate the function’s output for a given input x is the variable that represents a value at which to evaluate the function the letter f is the name of the function 7.2 revision of linear functions Work through the examples to revise what you have learned about linear functions. w orked examples A. Problem: (a) Copy and complete the table below for the functions defined by f (x) = x. f (-5) = -5 f (-4) = -4 f (-3) = -3 f (-2) = -2 f (-1) = -1 f (0) = 0 f (1) = 1 f (2) = 2 f (3) = 3 f (4) = 4 f (5) = 5 Solution: (a) x -5 -4 -3 -2 -1 0 1 2 3 4 5 f (x) -5 -4 -3 -2 -1 0 1 2 3 4 5 2153 TechMaths Eng G10 LB.indb 238 2015/10/22 3:41 PM chaPTer 7 FUNCTIONS AND GRAPHS 239 (b) Draw the graph of the function by plotting the coordinates on the Cartesian plane. (c) The x-intercept: (0; 0) (d) The y-intercept: (0 0) (e) Domain: x ? R (f) Range: y ? R x y –14 –12 –10 –6 –4 –2 2 0 4 6 8 10 12 14 –8 10 8 6 4 –2 –4 –6 –8 –10 2 w orked example B. Problem: A graph of a certain function is given below. x y –6 –4 –2 2 0 4 6 8 –8 12 10 8 6 4 –2 –4 –6 –8 –10 2 Copy and complete the table for this function by reading the values from the graph. Solution: x -5 -4 -3 -2 -1 0 1 2 3 4 5 f (x) -8 -6 -4 -2 0 2 4 6 8 10 12 (x; f (x)) (-5; -8) (-4; -6) (-3; -4) (-2; -2) (-1; 0) (0; 2) (1; 4) (2; 6) (3; 8) (4; 10) (5; 12) (b) x-intercept: (-1; 0) (c) y-intercept: (0; 2) (d) Domain: x ? R (e) Range: y ? R The domain is the set of all possible input values to which the rule applies. The range is the set of all possible output values to which the rule applies. 2153 TechMaths Eng G10 LB.indb 239 2015/10/22 3:41 PM 240 Technical Ma TheMaTicS Grade 10 exercises 1 Copy and complete the table for the functions defined by: (a) f (x) = -x (b) g (x) = x + 5 (c) h (x) = -x - 1 x -5 -4 -3 -2 -1 0 1 2 3 4 5 6 f (x) g (x) h (x) 2 Draw the graphs of each function in exercise 1 above on the same set of axes. 3 Complete the table below for the three functions drawn in exercise 2. Function x-intercept y-intercept Domain r ange f (x) = -x g (x) = x + 5 h (x) = -x - 1 4 Use the intercept method to sketch the graphs of the following functions: (a) y = x + 2 (b) y = x - 3 (c) y = 2x + 1 (d) y = -2x + 4 (e) x = y - 4 (f) x = y (g) y = -3x + 6 5 A graph of a certain function g (x) is given below. Copy the table below for the function g (x). By reading of corresponding x- and y-values of points on the graph of g (x), complete the table by writing down specific corresponding x- and y-values. x y –5 –6 –3 –2 –1 1 0 2 3 4 5 6 7 –4 6 7 5 4 3 2 –1 –2 –3 –4 –5 –6 –7 1 x y = g (x) 2153 TechMaths Eng G10 LB.indb 240 2015/10/22 3:41 PM chaPTer 7 FUNCTIONS AND GRAPHS 241 7.3 Quadratic function y = ax 2 w orked example Problem: Consider the function defined by f (x) = x 2 . Solution: Step 1: Calculate the output values of f (x) = x 2 for integer x-values -4 to +4. f (-3) = (-3 ) 2 = 9 f (0) = (0 ) 2 = 0 f (3) = (3 ) 2 = 9 f (-2) = (-2 ) 2 = 4 f (1) = (1 ) 2 = 1 f (4) = (4 ) 2 = 1 6 Step 2: Represent the function f(x) = x 2 by means of a table. x -4 -3 -2 -1 0 1 2 3 4 f (x) 16 9 4 1 0 1 4 9 16 Step 3: Draw the graph representing the function f (x) = x 2 . x y –6 –8 –4 –2 2 0 4 6 8 12 14 16 10 8 6 4 –2 –4 2 Step 4: Identify the shape of the graph. The graph opens upwards (shape). Step 5: Identify the intercepts of the graph. The graph intercepts the x-axis at one point (0; 0). The x-intercepts are also called the roots. An intercept is a point at which the graph intersects the x- or y-axis. 2153 TechMaths Eng G10 LB.indb 241 2015/10/22 3:41 PMRead More
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