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1. Write any two binomial expressions.
2
2
2. Write the irreducible factors of the terms of the algebraic expression: –5xy – 6x y + 18xy
1
3. What is the coefficient of (–a ) in – a b c?
2 3
2
2
4. Evaluate the following:
q − p
(a) , if p = –2 and q = –1 (b) x + 2x – 7, if x = 3
2
p
2
2
2
2
(c) (p + q) – 4pq, if p = 2 and q = –3 (d) 2x y + 2y z + 2z x, if x = –1, y = – 2, z = 1
5. Simplify the following:
(a) 3x + 4y – z + 2y – x (b) 4pq – 7r – pq + r

What is Equation?

Mother: To understand the concept of simple equation, let us take the
mathematical statements said by your dada ji to Aarav about Pihu's age. He
said that ‘Pihu was 13 years less than the double of her present age. Which is
equal to Aarav’s present age.’
Let us take a variable x for the unknown present age of Pihu.

Therefore, 13 years less than the double of the Pihu's present age = 2x – 13, which equals to the
Aarav’s present age. Since, Aarav is 5 years old at present.
So, we can write the above statement mathematically, as 2x – 13 = 5.
It is a simple equation with variable x.
So, we can say ‘an equation is a statement which states that two expressions are equal’.
Let us take some more statements and try to write them mathematically as simple equations.

(a) 5 added to x is 8, write it as 5 + x = 8
(b) 11 subtracted from m is 17, write it as m – 11 = 17

(c) 3 less from twice of x is 13 , write it as 2x – 3 = 13
x
(d) x divided by 5 gives 4, write it as = 4
5
Each mathematical statement has two expressions separated by equal sign (=). These mathematical
statements with equality sign are known as equations or we can say statement of equality.
In an equation, the equality sign (=) shows that the value of the expression to the left of the sign
(the left hand side or LHS) is equal to the value of the expression to the right of the sign (the right
hand side or RHS). In an equation 2x – 4 = 8, 2x – 4 is LHS and 8 is
RHS. Equal sign
2x – 4 = 8
Thus, we can conclude that an equation is a condition on a variable
which states that two expressions should have equal value and at LHS RHS
least one of the two expressions must contain a variable. Left Hand Side Right Hand Side

129 Simple Equations