Formula substitution

This chapter explores substitution in formulae or formulas. The chapter first looks at subsitition in simple equations or formulae then follows on to much harder expressions or formulae. Overall it is a very simple chapter to grasp.
In expressions especially formulae we use letters to represent values for example below formulae which represents the number of biscuits required for a certain number of people. p is the number of people and b represents biscuits for those number of people.

Suppose 32 people were at the party how many biscuits were required. We write and replace p with 32 as follows;

69 biscuits where required.
There are certain rules when carrying out substitutions.

…for example…


…for example…


…adding negative is the same as subtracting, for example…


…subtracting negative is the same as adding, for example;

In the following examples the x value will be substituted in the formulae to find out the outcome.

Example

Solve 4x-6 when x=-2

Example 2

Solve 5-x when x=-4

Example 3

Solve 16-3x when x=-3

Working with squares

Be careful when working with squares.

Try to remember these simple rules;



You might remember these rules from surds.

Example

Solve a² when a=7

Example 2

Solve 3a²/2 when a=4

Example

Solve 100-a² when a=8.