# Standard Identities

We shall now study three identities which are very useful in our work. These are obtained by multiplying a binomial by another binomial.

Let us consider the product

This is an identity, since the expression on the RHS is obtained from the LHS by actual multiplication. We may verify that for any value of a and any value of b, the values of two sides are equal.

Consider

The identities (I), (II) and (III) are known as standard Identities

Consider

Identity (IV) is the general form of the other three identities also.