Students can go through AP Board 8th Class Maths Notes Chapter 11 Algebraic Expressions to understand and remember the concepts easily.

## AP State Board Syllabus 8th Class Maths Notes Chapter 11 Algebraic Expressions

→ There are number of situations in which we need to multiply algebraic expressions.

→ A monomial multiplied by a monomial always gives a monomial.

→ While multiplying a polynomial by a monomial, we multiply every term in the polynomial by the monomial.

→ In carrying out the multiplication of an algebraic expression with another algebraic expression (monomial/ binomial/ trinomial etc.) we multiply term by term i.e. every term of the expression is multiplied by every term in the another expression.

→ An identity is an equation, which is true for-all values of the variables in the equation. On the other hand, an equation is true only for certain values of its variables. An equation is not an identity.

→ The following are identities:

I. (a + b)^{2} = a^{2} + 2ab + b^{2}

II. (a – b)^{2} = a^{2} – 2ab + b^{2}

III. (a + b) (a -b) = a^{2} – b^{2}

IV. (x + a) (x + b) = x^{2} + (a + b)x + ab

→ The above four identities are useful in carrying out squares and products of algebraic expressions. They also allow easy alternative methods to calculate products of numbers and so on.

Note:

We know that

(+) × (+) = +

(+) × (-) = –

(-) × (+) = –

(-) × (-) = +