Mammoth Memory

Graphs - Always make `y` the subject of the formula

The formula for a straight line is `y=mx+c`

If you are given the formula:

`3y-2x=8`

Always make `y`  the subject of the formula.

Always make y the subject of the formula to find the formula for a straight line graph

To make `y`  the subject of the formula follow this procedure:

`3y-2x=8`

Add `2x`  to both sides

`3y-2x+2x=8+2x`

`3y=8+2x`

 

Divide both sides by 3

`(3y)/3=(2x+8)/3`

Therefore: `y=2/3x+8/3`

 

Answer:

`y=2/3x+2\2/3`

 

This line can now be plotted on a graph as follows:

First lets calculate some points on the graph.

If

`x=-2` then `y` `=2/3(-2)+2\2/3` `=1.33`
`x=-1` then `y` `=2/3(-1)+2\2/3` `=2`
`x=0` then `y` `=2/3(0)+2\2/3` `=2.66`
`x=1` then `y` `=2/3(1)+2\2/3` `=3.33`
`x=2` then `y` `=2/3(2)+2\2/3` `=4`

Now draw the graph and mark out the above points:

Plotting points on a straight line graph

Now draw a straight line through these points.

Drawing a straight line through the points on the graph

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