Algebraic Expression│Class 7 RS Aggarwal │Introduction of chapter 6│Class 7 chapter 6 in hindi
What is an Algebraic Expression?
An algebraic expression in mathematics is an expression which is made up of variables and constants, along with algebraic operations (addition, subtraction, etc.). Expressions are made up of terms. They are also termed algebraic equations.
Examples
3x + 4y – 7, 4x – 10, etc.
These expressions are represented with the help of unknown variables, constants and coefficients. The combination of these three (as terms) is said to be an expression. It is to be noted that, unlike the algebraic equation, an algebraic expression has no sides or equal to sign. Some of its examples include
- 3x + 2y – 5
- x – 20
- 2x2 − 3xy + 5
Variables, Coefficient & Constant
In Algebra we work with Variable, Symbols or Letters whose value is unknown to us.
In the above expression (i.e. 5x – 3),
- x is a variable, whose value is unknown to us which can take any value.
- 5 is known as the coefficient of x, as it is a constant value used with the variable term and is well defined.
- 3 is the constant value term which has a definite value.
The whole expression is known to be the Binomial term, as it has two unlikely terms.
Types of Algebraic expression
There are 3 main types of algebraic expressions which include:
- Monomial Expression
- Binomial Expression
- Polynomial Expression
Monomial Expression
An algebraic expression which is having only one term is known as a monomial.
Examples of monomial expression include 3x4, 3xy, 3x, 8y, etc.
Binomial Expression
A binomial expression is an algebraic expression which is having two terms, which are unlike.
Examples of binomial include 5xy + 8, xyz + x3, etc.
Polynomial Expression
In general, an expression with more than one terms with non-negative integral exponents of a variable is known as a polynomial.
Examples of polynomial expression include ax + by + ca, x3 + 2x + 3, etc.
Other Types of Expression:
Apart from monomial, binomial and polynomial types of expressions, an algebraic expression can also be classified into two additional types which are:
- Numeric Expression
- Variable Expression
Numeric Expression
A numeric expression consists of numbers and operations, but never include any variable. Some of the examples of numeric expressions are 10 + 5, 15 ÷ 2, etc.
Variable Expression
A variable expression is an expression which contains variables along with numbers and operation to define an expression. A few examples of a variable expression include 4x + y, 5ab + 33, etc.
Algebraic expression for Class 7
In Class 7, students will come across the terms of algebraic equations such as:
- Coefficient of a term
- Variables
- Constant
- Factors of a term
- Terms of equations
- Like and Unlike terms
Example of using these terms are given below.
If 2x2+3xy+4x+7 is an algebraic expression.
Then, 2x2, 3xy, 4x and 7 are the terms
Coefficient of term x2 = 2
Constant term = 7
Example of like and unlike terms:
Like terms: 2x and 3x
Unlike terms: 2x and 3y
Factors of a term:
If 3xy is a term, then its factors are 3, x and y.
Monomial, Binomial & Trinomial
Also, in grade 7 we will learn about types of expressions, such as monomial, binomial and trinomial. Let us see examples of each.
Monomial: 2x
Binomial: 2x+3y
Trinomial: 2x+3y+9
Addition and Subtraction of Algebraic Expressions
We can add and subtract like terms easily.
Example: Add 3x + 5y – 6z and x – 4y + 2z.
By adding both the expressions we get;
(3x + 5y – 6z) + (x – 4y + 2z)
Separating the like terms and adding them together:
(3x + x) + (5y – 4y) + (-6z + 2z)
4x + y – 4z
Formulas
The general algebraic formulas we use to solve the expressions or equations are:
- (a + b)2 = a2 + 2ab + b2
- (a – b)2 = a2 – 2ab + b2
- a2 – b2 = (a – b)(a + b)
- (a + b)3 = a3 + b3 + 3ab(a + b)
- (a – b)3 = a3 – b3 – 3ab(a – b)
- a3 – b3 = (a – b)(a2 + ab + b2)
- a3 + b3 = (a + b)(a2 – ab + b2)
Solved Problem
| Example: Simplify the given expressions by combining the like terms and write the type of Algebraic expression. (i) 3xy3 + 9x2 y3 + 5y3x (ii) 7ab2 c2 + 2a3 b2 − 3abc – 5ab2 c2 – 2b2 a3 + 2ab (iii) 50x3 – 20x + 8x + 21x3 – 3x + 15x – 41x3 Solution: Creating a table to find the solution:
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