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5. Draw the lines of symmetry in the following figures.
11 Algebraic Expressions
a. b. c.

INTRODUCTION

In arithmetic, we deal with specific numbers and use the symbols 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 to represent
them. We use the four fundamental operations, namely, addition(+), subtraction(-). multiplication (x) and divi-
d. f. sion (+) on specific numbers and obtain number expressions.
On the basis of certain observations, we obtain a general result, called ajormula.
Consider the following example:
The perimeter of a square is given by perimeter = 4 x side.
If we represent the perimeter by the letter p and the length of the side by the letter s, we can write
p = 4 x s.
This rule is true for all systems of units and for all possible values of the length of the side of the square.
When s = 2, we get p = 4 x 2 = 8.
Whens= 3, we get p = 4 x 3 = 12, and so on.
1. Take a sheet of paper and fold it into two halves. Punch a hole. Open the sheet. Are the two holes Clearly, p ands represent numbers.
symmetrical about the fold? What is the fold of the paper called? Thus, the generalized results of arithmetic are known as formulae.
In a formula, we use letters to represent numbers.
2. Draw three objects from your day to day life that have no line of symmetry.
Such letters are known as literal numbers.
3. What is the another name that you can give to the line of symmetry of ALGEBRA
a. an isosceles triangle b. circle c. parallelogram.
Algebra is generalized arithmetic in which numbers are represented by letters, known as literal numbers or
simply literals.
Since literals are also numbers, they obey all the rules of addition, subtraction, multiplication and division.

OPERATIONS ON LITERALS AND NUMBERS

1.ADDITION (i) The sum of a literal x and a number 5 is x + 5.
(ii) y more than x is written as x + y.
(iii) For any literals a, b, c, we have:
a+ b = b + a; a+ 0 = 0 + a= a; and (a+ b) + c =a+ (b + c).
2.SUBTRACTION (i) 5 less than a literal xis x -5.
(ii) y less than xis x -y.
3. MULTIPLICATION 4 times xis 4 xx, written as 4x.
(ii)The product of x and y is xx y, written as x • y or xy.
(iii)For any literals a, b, c we have:
a × O = 0 × a = O; a × 1 = 1 × a = a; a × b =b × a;
(ab)c = a(bc): a(b + c) =ab+ ac

x
4.DIVISION (i) x divided by y is written as
x y
(ii) x divided by 7 is
7 30
(iii) 30 divided by x is
x