The equation of a line from its graph

The Maths Habit

Which is the odd one out? Why?

A
B
C
D
D is curved. A is the only one going across. B is the only one going up.

123456123456780xyPQ
Write the coordinates of P. (4, 2)
Write the coordinates of Q. (0, 5)

123456123456780xy
Coordinates
Two numbers that give a point: across, then up.
123456123456780xy
Horizontal
Going straight across.
123456123456780xy
Vertical
Going straight up and down.
123456123456780xy
Equation of a line
A rule that every point on the line fits.

Find the equation of the line.

123456123456780xyxy444135
1Read three points.
2Find the rule.
3Write the equation.

Every x is 4.

x = 4

Find the equation of the line.

123456123456780xyx125y333
1Read three points.
2Find the rule.
3Write the equation.

Every y is 3.

y = 3

Find the equation of the line.

123456123456780xyxy444135
1Read three points.
2Find the rule.
3Write the equation.

Every x is 4.

x = 4
1Read three points.
2Find the rule.
3Write the equation.

Find the equation of the line.

123456123456780xyx023y666

Every y is 6.

y = 6

Find the equation of the line.

123456123456780xyxy444135
1Read three points.
2Find the rule.
3Write the equation.

Every x is 4.

x = 4
1Read three points.
2Find the rule.
3Write the equation.

Find the equation of the line.

123456123456780xyx111y257

Every x is 1.

x = 1

Find the equation of the line.

123456123456780xyxy444135
1Read three points.
2Find the rule.
3Write the equation.

Every x is 4.

x = 4
1Read three points.
2Find the rule.
3Write the equation.

Find the equation of the line.

123456123456780xyxy245222

Every y is 2.

y = 2

What do you add to each x to get its y?

x124
y457
Add 3: 1 + 3 = 4, 2 + 3 = 5, 4 + 3 = 7

Find the equation of the line.

123456123456780xyxy023356
1Read three points.
2Find the rule.
3Write the equation.

Each y is x add 3.

y = x + 3

Find the equation of the line.

123456123456780xyx124y346
1Read three points.
2Find the rule.
3Write the equation.

Each y is x add 2.

y = x + 2

Find the equation of the line.

123456123456780xyxy023356
1Read three points.
2Find the rule.
3Write the equation.

Each y is x add 3.

y = x + 3
1Read three points.
2Find the rule.
3Write the equation.

Find the equation of the line.

123456123456780xyx012y456

Each y is x add 4.

y = x + 4

Find the equation of the line.

123456123456780xyxy023356
1Read three points.
2Find the rule.
3Write the equation.

Each y is x add 3.

y = x + 3
1Read three points.
2Find the rule.
3Write the equation.

Find the equation of the line.

123456123456780xyx124y235

Each y is x add 1.

y = x + 1

Find the equation of the line.

123456123456780xyxy023356
1Read three points.
2Find the rule.
3Write the equation.

Each y is x add 3.

y = x + 3
1Read three points.
2Find the rule.
3Write the equation.

Find the equation of the line.

123456123456780xyxy035257

Each y is x add 2.

y = x + 2

Thumbs up for yes. Thumbs down for no.

  1. Is (3, 5) on the line y = x + 2?

    Yes: 3 + 2 = 5

  2. Is (4, 2) on the line x = 4?

    Yes: its x is 4

  3. Is (2, 6) on the line y = x + 3?

    No: 2 + 3 = 5

  4. Is (5, 3) on the line y = 5?

    No: its y is 3

  5. Is (1, 7) on the line y = x + 6?

    Yes: 1 + 6 = 7

The equation of a line from its graph worksheet, page 1

The equation of a line from its graph worksheet, page 2

Answer sheet

  1. A line goes through (0, 1), (1, 3), (2, 5). Find its equation.

    y = 2x + 1

  2. A line goes through (0, 7), (1, 6), (2, 5). Find its equation.

    y = 7 − x

  3. What is the equation of the x axis?

    y = 0

  4. Where does the line y = x + 9 cross the y axis?

    (0, 9)

  1. These three points are on a line. Find the equation of the line.

    y = 6
    x134y666=

  2. Complete the table for line A. Find its equation.

    y = x + 2
    123456123456780xyABxyy = x +

  3. Find the equation of line B.

    y = x + 5
Exit tickets to print