© Daniel Holloway
We know that all linear graphs appear in
the form y = mx + c where m is the gradient
of the line and c is the point at which the yaxis is intercepted
y
5
-5
0
5 x
Suppose we wanted to
find the equation of the
line shown:
1. Find the point where
the line crosses the yaxis
in this case, it is (+)2
therefore, c = 2
2. Find the gradient of
the line
in this case, it is (+)3
therefore, m = 3
3. Put the two pieces of
information together
the equation: y = 3x + 4
Give the equations of the following lines:
y
5
-5
0
Equation:
y=
= ⅓x
5x +- 1
1.5x
5 x
y
5
O
5
x
We can solve
simultaneous
equations
graphically as well
as algebraically.
We simply need to
use the same m
and c rules to plot
the lines and find
where the points
meet
Take the simultaneous
equations
y=x+5
y = 2x + 4
y
5
O
5
x
This is how we can
solve the pair of
equations graphically
y = 2x + 4
y
y=x+3
1.
Plot points and draw in the
line for one equation
2. Complete the same for the
other equation
The point at which the two lines
cross is our answer. Read the x
and y values on the grid to find:
x=1
y=6
5
O
5
x