An Introduction to Straight Line Graphs

Drawing straight line graphsfrom their equations.

Investigating different straightline graphs.

y = x + 7

y = 3x – 5

y = 9 – 2x

x

y

x

y

x

y

x

y

y = 2x2 4

-4 1 2

10 -8

5

4 6 15 1

11 13

8 -6

2 5 1

1 10 -2

3 4 5

3 1 -1 9

0

Revising Substitution

-10 -8 -6 -4 -2 2 4 6 8 10

10

8

6

4

2

-2

-4

-8

-10

-6

Plotting Co-ordinates

(1,2)

x value y value

x

y

(2, 4)(5, 10)(-4,-8)

We have nowrevised substitutionand co-ordinates.How could we drawthe graph y = 2x?

Introduction to Straight Line Graphs - Solutions

x -7 0 1 4 6

y -11 3 5 11 15

x -5 -2 2 3 5

y -4 2 10 12 16

a) y = 2x + 3 b) y = 2x + 6

c) y = 2x – 4 d) y = 17 – 2x

Extension: Where does each graph intersect the y axis?

Plot the points to draw the graphs.

x 0 2 3 5 6

y -4 0 2 6 8

x 0 2 4 6 8

y 17 13 9 5 1

Solutions

2

6

8

10

4

12

14

-4

-8

-10

-6

-12

-14

2-6 42-2-4 6 8-8

y = 2x + 3

y = 2x + 6y = 2x – 4

y = x – 10

y = 2x – 7

What do the graphsy = 2xy = 2x + 3y = 2x + 6 y = 2x – 4 y = 2x – 7 have in common?

What are the

differences?

x

y

More Substitution

Substitution: we replace the variables in the equation with numbers.

Replace the x with a number, for example, 3.

Now our equation is: y = 2 3

We can now find the value of y.

Equation: y = 2x (This is the same as y = 2 x.)