Download An Introduction to Straight Line Graphs

An Introduction to Straight
Line Graphs
Drawing straight line graphs
from their equations.
Investigating different straight
line graphs.
Revising Substitution
y = 2x
x
-4
1
2
5
y
-8
2
4
10
x
4
6
y
11
y=x+7
y = 3x – 5
x
2
5
1
y
1
10
-2
y = 9 – 2x
8
-6
13
15
1
x
3
4
5
0
y
3
1
-1
9
Plotting Co-ordinates
y
10
x value
y value
8
6
(1,2)
(2, 4)
(5, 10)
(-4,-8)
We have now
revised substitution
and co-ordinates.
How could we draw
the graph y = 2x?
4
2
-10
-8
-6
-4
-2
2
-2
-4
-6
-8
-10
4
6
8
10 x
Introduction to Straight Line Graphs - Solutions
Plot the points to draw the graphs.
b) y = 2x + 6
a) y = 2x + 3
x
-7
0 1
y
-11 3 5
4
6
11 15
c) y = 2x – 4
x
-5 -2 2
y
-4 2
3
5
10 12 16
d) y = 17 – 2x
x
0
2 3
5
6
x
0
2
4
6
8
y
-4 0 2
6
8
y
17 13 9
5
1
Extension: Where does each graph intersect the y axis?
y
14
Solutions
12
10
What do the graphs
y = 2x
y = 2x + 3
y = 2x + 6
y = 2x – 4
y = 2x – 7
have in common?
8
6
y = 2x + 6
y = 2x – 4
4
y = 2x – 7
2
-8
-6 -4
2
-2
4
6
2
What are the
-4
differences?
-6
-8
y = 2x + 3
-10
-12
-14
y = x – 10
8 x
More Substitution
Substitution: we replace the variables in the equation with
numbers.
Equation: y = 2x (This is the same as y = 2  x.)
Replace the x with a number, for example, 3.
Now our equation is: y = 2  3
We can now find the value of y.