Saturday, December 16

Making Subjects. How to Make x The Subject of a Formula (1 Inverse Only)

Making a letter the subject of the formula is a bit like solving an equation. To make another letter the subject of a formula you can follow these simple steps:

Step 1: Swap the left hand side (LHS) of the formula with the right hand side (RHS) of the formula.

Step 2: Apply the inverse operations to both sides of your formula. This will make the required letter the subject.

Let’s take a look at some simple examples (all these require only 1 inverse operation).

Example 1

Make x the subject of this formula.

y = x + 7

First of all swap the left hand side with the right hand side.

x + 7 = y

Now on the LHS you are adding on 7 to x. So you must do the inverse to add 7 and take 7 off both sides.

x = y -7

So now x is the subject as you now have a formula for x.

Example 2

Make x the subject of this formula.

y = 8x

First of all swap the left hand side with the right hand side.

8x = y

Now since x is being multiplies by 8 you need to divide both sides by 8. This gives

y = x/8

Example 3

Make x the subject of this formula:

y = x – z

First of all swap the left hand side of the formula with the right hand side of the formula.

x – z = y

Now on the left hand side z is being taken away so you need to apply the opposite operation to both sides and add on z.

This gives x = y + z.

Let’s take a look at one last example:

Make x the subject of this formula

y =x/3z

Swapping the left hand side and right hand side gives:

x/3z = y

So x is being divided by 3z so do the opposite and multiply by 3z

This gives:

x = 3yz.