An equation states that two expressions are equal in value, eg .
Solving an equation means finding the value or values for which the two expressions are equal. This means equations are not always true. In the example above, , the only correct solution for is 2.
An identity is an equation which is always true, no matter what values are substituted. is an identity because will always simplify to regardless of the value of . Identities can be written with the sign ≡, so the example could be written as .
Show that is the solution of the equation
BIDMAS means the multiplication is carried out before the addition:
Are the following an identity or an equation?