Algebraic Expression of Class 7
Algebraic expressions rules
When two or more quantities are united together the result is called their sum. There are 4 simple rules to obtain the sum.
Rule 1: When 2 positive quantities are added the sum is a positive quantity
(+a) + (+b) = + (a + b)
e.g.: (+7a) + (+5a) = + (7a + 5a) = +12a
Rule 2: When 2 negative quantities are added together the sum is a negative quantity.
(–a) + (–b) = – (a + b)
e.g.: (– 8x) + (– 6x) = – (8 + 6)x = – 14x
Rule 3: When a negative quantity is added to a positive quantity, the sign of the result is positive or negative according as the absolute value is less or greater than that of the positive quantity and the absolute value of the result is always equal to the difference between the absolute values of the quantities.
If a > b (– a) + (+ b) = – (a – b) Eg: (– 7a) + (+ 3a) = – 4a
If a < b (– a) + (+ b) = + (b – a) E.g.: (– 2a) + ( + 7a) = + 5a
Column method for addition of Algebraic expressions:
Write each expression in a separate row such that their like terms are arranged one below the other in a column. Then the terms are added column wise.
Horizontal method for addition of algebraic expressions:
We add two or more expressions by collecting the like terms together and then simplifying.
TRUE FALSE QUESTIONS
question1.The binomial is an algebraic expressions with two terms
question2.When 2 negative quantities are added together the sum is a positive quantity.
question3.A polynomial of degree 2 is called a quadratic polynomial.
question4.The number of terms in the expression 8x2yz is 2