1. STRAIGHT LINE GRAPHS
y = mx + c

2. STRAIGHT LINE GRAPHS ALL are of the form y = mx +c
m is the GRADIENT of the line
c is the ‘y intercept’

3. STRAIGHT LINE GRAPHS We must to be able to DRAW THE GRAPHS
FIND THE EQUATION FROM A GRAPH

4. STRAIGHT LINE GRAPHS DRAWING THE GRAPHS WE NEED TO IDENTIFY TWO POINTS
POINT 1 IS THE y INTERCEPT
POINT 2 IS FOUND BY SUBSTITUTING A VALUE FOR x INTO THE FUNCTION
DRAWING THE GRAPHS

5. If we use the example y = 3x - 1
STRAIGHT LINE GRAPHS
If we use the example y = 3x - 1
The y intercept is -1
REMEMBER (y = mx + c)
So point 1 is (0,-1)
If we substitute x = 1
then y = 3 - 1
so y = 2
So point 2 is (1,2)

6. STRAIGHT LINE GRAPHS NOTE THE TWO POINTS CHOSEN
THE FINISHED GRAPH LOOKS LIKE THIS
NOTE
THE TWO POINTS CHOSEN

7. NOW WE MUST LEARN HOW TO FIND AN EQUATION FROM A GRAPH
STRAIGHT LINE GRAPHS
NOW WE MUST LEARN HOW TO FIND AN EQUATION FROM A GRAPH

8. STRAIGHT LINE GRAPHS SO ‘C’ IS -4 IF WE USE THIS GRAPH
WE CAN SEE THAT THE LINE CROSSES THE Y AXIS AT THE POINT (0,-4)
SO ‘C’ IS -4

9. STRAIGHT LINE GRAPHS
The gradient (m) is defined as

10. STRAIGHT LINE GRAPHS We need to find m (the gradient)
We need to find the change in y
We need to find the change in x
The change in y is 4
The change in x is 2

11. STRAIGHT LINE GRAPHS So m = 2 Since the gradient is defined as

12. We know the equation of the line is
STRAIGHT LINE GRAPHS
STRAIGHT LINE GRAPHS
As y = mx + c
We know the equation of the line is
y = 2x - 4

13. STRAIGHT LINE GRAPHS Click here to draw graphs
Click here to re-start the presentation