In this activity, we will use straight line graphs in the form y = mx + c. We will be able to see if a given coordinate lies on the lines given.

**Recap**

For a straight line graph we use the form:

**y = mx + c**

**m **is the **gradient**

**c **is the **y intercept**

Let's have a look at a typical question!

__Example__

Does the point P (2, 4) lie on the straight line y = 3x - 2?

**Answer**

The point P (2, 4) means when x = 2, y = 4

If it lies on the line y = 3x - 2 then we can substitute these values in and the equation should be true!

If not, then the point cannot lie on the line!

We have** y = 3x - 2**

Let's put our x and y values in there from point P:

y = 4 and x = 2

4 = (3x2) - 2

4 = 6 - 2

4 = 4 it's correct!

Therefore, **the point P does lie on the line y = 3x - 2**

If this had** not been** correct, then the point P would **not lie **on the line!

Let's try some questions.