Page 139 - ICSE Math 7

EXERCISE 12.1

1. Write the algebraic expressions for the following statements.

(a) 18 multiplied by x and 25 subtracted from the result is 191.
(b) 56 added to 2y gives 84.
(c) q multiplied with –6 gives 114.

(d) –3 multiplied by y when added to 18 gives 26.
2. Identify the monomials, binomials and trinomials among the following.
2
2
(a) 7xy – a (b) 14 q (c) –13 (d) p q – q p
17 2 2
x y
(e) 9 – xyz + y 2 (f) ab – a 2 (g) x + y – 10 (h) 13 2 2
4 9 5
3. Identify the pairs of like terms among the following.
7
3
2
(a) 6x, –6y (b) 5x y, 15yx 2 (c) ab, – ab (d) 7 ab, b
5 9 9
2
2
(e) 19y , –3y (f) 2ab, 3abc
4. Find the coefficient of x in each of the following terms.
x yz
(a) 3 x (b) –13xy (c) 7 3 (d) –xyz
16 9
5. Which of the following algebraic expressions are polynomials? If so, find their degree.
3
2
2
6
(a) a + 1 (b) x + 3x + 5 (c) 9x + – x 3 (d) p – 1
a x
6 5
3
3
2
(e) 5x – 7x + 9 (f) a + a – + a
a
x
2
4
3
6. For the algebraic expression 4x – x + 3x – – 9 , answer the following.
5 11
(a) How many terms are there in the given expression?
(b) Which is the constant term?
2
4
3
(c) What are the coefficients of x , x and x ?
(d) What is the degree of the given polynomial?
Addition
Addition of like terms
The sum of two or more like terms is a term whose numerical coefficient is the sum of the numerical
coefficients of the given terms. Example:
3
(a) 4x + 9x = (4 + 9)x = 13x (b) 2ab + (–13ab) + ab = 2 13−   + 3   ab = – 52 ab
5  5  5
Addition of unlike terms
Two unlike terms can never be added to get a single term. So, we just write the unlike terms as the
terms of the algebraic expression with an addition sign. Example: the sum of 3ab and 2pq is 3ab + 2pq.

Addition of polynomials

To add the given polynomials, arrange the like terms together and add them. Also, add the unlike
terms by writing them as the terms of the algebraic expression. This method is known as horizontal

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