Exercise 3.1

Exercise 3.1

1. Fill in the blanks:

(i) The variable in the expression 16x − 7 is x.

(ii) The constant term of the expression 2y − 6 is –6.

(iii) In the expression 25m + 14n, the type of the terms are variable terms.

(iv) The number of terms in the expression 3ab + 4c –9 is three.

(v) The numerical co-efficient of the term −xy is – 1.

2. Say True or False.

(i) x + ( −x) = 0 (True)

(ii) The co-efficient of ab in the term 15abc is 15. (False)

(iii) 2pq and − 7qp are like terms (True)

(iv) When y = −1, the value of the expression 2y − 1 is 3 (False)

3. Find the numerical coefficient of each of the following terms: −3yx, 12k, y, 121bc, − x, 9pq, 2ab

–3yx, 12k, y, 121bc, – x, 9pq, 2ab

The numerical coefficients –3, 12, 1, 121, –1, 9, 2

4. Write the variables, constants and terms of the following expressions.

(i) 18 + x − y (ii) 7p − 4q + 5 (iii) 29x + 13y (iv) b + 2

Answer: 

5. Identify the like terms among the following : 7x, 5y, −8x, 12y, 6z, z, −12x, −9y, 11z.

Like terms :

x terms : 7x, –8x, –12x

y terms : 5y, 12y, –9y

z terms : 6z, z, 11z

6. If x = 2 and y = 3, then find the value of the following expressions

(i) 2x – 3y (ii) x + y (iii) 4y – x (iv) x + 1 – y

x = 2, y = 3

i) 2x – 3y = 2(2) – 3(3)

               = 4 – 9 = –5

ii) x + y = 2 + 3 = 5

iii) 4y – x = 4 (3) – 2 = 12 – 2 = 10

iv) x + 1 – y = 2 + 1 – 3 = 3 – 3 = 0

Objective type questions

7. An algebraic statement which is equivalent to the verbal statement “Three times the sum of x and y” is

(i) 3(x + y)

(ii) 3 + x + y

(iii) 3x + y

(iv) 3 + xy

Answer : (i) 3(x +y)

8. The numerical co-efficient of −7mn is

(i) 7

(ii) −7

(iii) p

(iv) −p

Answer : ii) –7

9. Choose the pair of like terms

(i) 7p, 7x

(ii) 7r, 7x

(iii) −4x, 4

(iv) −4x, 7x

Answer : (iv) –4x, 7x

10. The value of 7a − 4b when a = 3, b = 2 is

(i) 21

(ii) 13

(iii) 8

(iv) 32

Answer : (ii) 13

ANSWERS

EXERCISE-3.1

1. (i) x

(ii) −6

(iii) unlike

(iv) three

(v) −1

2. (i) True (ii) False (iii) True (iv) False

3. −3,12, 1,121, −1,9,2.

4. 

5. 

6. (i) –5 (ii) 5 (iii) 10 (iv) 0

 Objective type questions

7. (i) 3(x+y)

8. (ii) –7

9. (iv) −4x , 7x

10. (ii) 13