# The Linear function. 1. Investigate the effect of m on the graph of y = ax 2. Work with gradient and parallel and perpendicular lines. 3. Investigate.

## Presentation on theme: "The Linear function. 1. Investigate the effect of m on the graph of y = ax 2. Work with gradient and parallel and perpendicular lines. 3. Investigate."— Presentation transcript:

The Linear function

1. Investigate the effect of m on the graph of y = ax 2. Work with gradient and parallel and perpendicular lines. 3. Investigate the effect of c on the graph of y = ax + q. 4. Use linear equations to solve real life problems

Drawing graphs 1 Consider the function y=2x+1 1. TABLE METHOD Choose values for x and substitute to find the corresponding y- values. Plot the (x;y) coordinate pairs. x012 y 135

Drawing graphs 2 Consider the function y=2x+1 2. DUAL INTERCEPT METHOD Find the value of the x-intercept (let y=0) and plot this point. Find the value of the y-intercept (let x=0) and plot this point x-int: 0 = 2x+1y-int: y=2(0)+1 -1=2x = 0+1 -½ =x y = 0 Now connect the two intercepts to form a straight line.

Drawing graphs 3 Consider the function y=2x+1 3. GRADIENT INTERCEPT METHOD From the equation, determine the y-intercept (c-value) Plot the y-intercept and use the “rise over run” method to use the gradient of the graph to find one other point. Join these points to form a straight line. y-int = 1… then rise 2 and run 1

Investigate the effect of m on the graph of y = mx The equation of the straight line graph can be written as: Standard equation: y=ax+q General equation: The gradient of a line (a):

Investigate the effect of m on the graph of y = mx A decreasing function: ( m is negative) An increasing function: ( m is positive) A greater m value will have a “steeper slope” Worked example: find the gradient of the line which passes through (-2;3) and (1;9).

Work with gradient and parallel and perpendicular lines. Use subscript to indicate the gradient of different lines: represents the gradient of line AB and line CD Parallel and Perpendicular lines: B A D C y x A B C D y x

Worked Example: Determine k if the line joining P(5;7) and R(-3;-1) is perpendicular to the line joining A(7;-11) and B(k;-9).

Test your knowledge Question 1 Determine k if the line joining A(2; 1) and P(5; 7) is parallel to the Line through R( k; 6) and T(-3; -2) Answer A) k = -3B) k = 2C) k = 1 D) k = 4

3. Investigate the effect of q on the graph of y = ax + q. A line parallel with the y – axis is: x = c i.e. x = 4 and its gradient =0 A line parallel with the x – axis is: y = c i.e. y = 2 and its gradient is undefined y = c, is a line parallel with the x axis and cut the y – axis at y = c m = gradient and c = the y – intercept. c 0

3. Investigate the effect of a on the graph of y = ax + q. To determine the y – intercept, put x = 0 To determine the x –intercept, put y = 0 c = 0 c y=3 c x = 4 y y y x x x

To determine the equation of a linear function Determine the gradient: if:and If q (y-int) is given, substitute into your equation If a co – ordinate pair of one point is given, substitute into the given equation and solve for q.

Worked Example: Determine the equation of a line that passes through (-2;-3) and (-7;-13)

Test your knowledge Question 2 Determine the equation of a line that passes through (1; 6) and (-2; 3) Answer A) y = x -3B) y = x +5C) y = - x +3 D) y = -2x +4

4. Use linear equations to solve real – life problems Example: Mr. Naidoo uses wooden boards as shelves for plant holders. Each board rests on supports fixed at equal distances along the plank. Mr Flowers finds that if the supports are 50 cm apart, he can load 110 kg on a plank. If the supports are 100cm apart, he can load only 10kg.on the plank. a) Write down two pairs of coordinates (distance; Load) b) If the relationship between distance in centimeters and load in kilograms is a linear function, find the equation of the function. c) Make a graphical representation of the function.

4. Use linear equations to solve real – life problems Solution: a) (50;110) and (100;10) y = -2x + 210 105 210 y x

Test your knowledge Question 3 Determine the equation of a line through (-1; 2) and (-3; -2) Answer A) y = 3x +4 B) y = - 2x + 5 C) y = 2x – 3 D) y = 2x +4