NCERT Class 7 Maths Chapter 12 Algebraic Expressions Exercise 12.3


Chapter 12 Algebraic Expressions Exercise 12.3

Question 1: If m = 2, find the value of:
(i) m - 2
Answer:

= m = 2
= 2 - 2
= 0

(ii) 3m - 5
Answer:

= m = 2
= (3 × 2) - 5
= 6 - 5
= 1

(iii) 9 - 5m
Answer:

= m = 2
= 9 - (5 × 2)
= 9 - 10
= -1

(iv) 3m² - 2m – 7
Answer:

= m = 2
= (3 × 2²) - (2 × 2) – 7
= (3 × 4) - (4) - 7
= 12 - 4 -7
= 12 - 11
= 1

(v) (5m/2) - 4
Answer:

= m = 2
= ((5 × 2)/2) - 4
= (10/2) - 4
= 5 - 4
= 1

Question 2: If p = -2, find the value of:
(i) 4p + 7
Answer:

= p = -2
= (4 × (-2)) + 7
= -8 + 7
= -1

(ii) -3p² + 4p + 7
Answer:

= p = -2
= (-3 × (-2)²) + (4 × (-2)) + 7
= (-3 × 4) + (-8) + 7
= -12 - 8 + 7
= -20 + 7
= -13

(iii) - 2p³ - 3p² + 4p + 7
Answer:

= p = -2
= (-2 × (-2)³) - (3 × (-2)²) + (4 × (-2)) + 7
= (-2 × -8) - (3 × 4) + (-8) + 7
= 16 - 12 - 8 + 7
= 23 - 20
= 3

Question 3: Find the value of the following expressions, when x = -1:
(i) 2x - 7
Answer:

= x = -1
= (2 × -1) - 7
= -2 - 7
= -9

(ii) - x + 2
Answer:

= x = -1
= - (-1) + 2
= 1 + 2
= 3

(iii) x² + 2x + 1
Answer:

= x = -1
= (-1)² + (2 × -1) + 1
= 1 - 2 + 1
= 2 - 2
= 0

(iv) 2x² - x - 2
Answer:

= x = -1
= (2 × (-1)²) - (-1) – 2
= (2 × 1) + 1 - 2
= 2 + 1 - 2
= 3 - 2
= 1

Question 4: If a = 2, b = -2, find the value of:
(i) a² + b²
Answer:

a = 2, b = -2
= (2)² + (-2)²
= 4 + 4
= 8

(ii) a² + ab + b²
Answer:

a = 2, b = -2
= 2² + (2 × -2) + (-2)²
= 4 + (-4) + (4)
= 4 - 4 + 4
= 4

(iii) a² - b²
Answer:

a = 2, b = -2
= 22 - (-2)2
= 4 - (4)
= 4 - 4
= 0

Question 5: When a = 0, b = -1, find the value of the given expressions:
(i) 2a + 2b
Answer:

a = 0, b = -1
= (2 × 0) + (2 × -1)
= 0 - 2
= -2

(ii) 2a² + b² + 1
Answer:

a = 0, b = -1
= (2 × 0²) + (-1)² + 1
= 0 + 1 + 1
= 2

(iii) 2a²b + 2ab² + ab
Answer:

a = 0, b = -1
= (2 × 0² × -1) + (2 × 0 × (-1)²) + (0 × -1)
= 0 + 0 +0
= 0

(iv) a² + ab + 2
Answer:

a = 0, b = -1
= (0²) + (0 × (-1)) + 2
= 0 + 0 + 2
= 2

Question 6: Simplify the expressions and find the value if x is equal to 2
(i) x + 7 + 4 (x - 5)
Answer:

= x = 2
= x + 7 + 4x - 20
= 5x + 7 - 20
= (5 × 2) + 7 - 20
= 10 + 7 - 20
= 17 - 20
= -3

(ii) 3 (x + 2) + 5x – 7
Answer:

= x = 2
= 3x + 6 + 5x - 7
= 8x - 1
= (8 × 2) - 1
= 16 - 1
= 15

(iii) 6x + 5 (x - 2)
Answer:

= x = 2
= 6x + 5x - 10
= 11x - 10
= (11 × 2) - 10
= 22 - 10
= 12

(iv) 4(2x - 1) + 3x + 11
Answer:

= x = 2
= 8x - 4 + 3x + 11
= 11x + 7
= (11 × 2) + 7
= 22 + 7
= 29

Question 7: Simplify these expressions and find their values if x = 3, a = -1, b = -2.
(i) 3x - 5 - x + 9
Answer:

= x = 3
= 3x - x - 5 + 9
= 2x + 4
= (2 × 3) + 4
= 6 + 4
= 10

(ii) 2 - 8x + 4x + 4
Answer:

= x = 3
= 2 + 4 - 8x + 4x
= 6 - 4x
= 6 - (4 × 3)
= 6 - 12
= -6

(iii) 3a + 5 - 8a + 1
Answer:

= a = -1
= 3a - 8a + 5 + 1
= -5a + 6
= - (5 × (-1)) + 6
= - (-5) + 6
= 5 + 6
= 11

(iv) 10 - 3b - 4 - 5b
Answer:

= b = -2
= 10 - 4 - 3b - 5b
= 6 - 8b
= 6 - (8 × (-2))
= 6 - (-16)
= 6 + 16
= 22

(v) 2a - 2b - 4 - 5 + a
Answer:

= a = -1, b = -2
= 2a + a - 2b - 4 - 5
= 3a - 2b - 9
= (3 × (-1)) - (2 × (-2)) - 9
= -3 - (-4) - 9
= -3 + 4 - 9
= -12 + 4
= -8

Question 8: (i) If z = 10, find the value of z³ - 3(z - 10).
Answer:

= z = 10
= z³ - 3z + 30
= (10)³ - (3 × 10) + 30
= 1000 - 30 + 30
= 1000

(ii) If p = - 10, find the value of p² - 2p – 100
Answer:

= p = -10
= p² - 2p - 100
= (-10)² - (2 × (-10)) - 100
= 100 + 20 - 100
= 20

Question 9: What should be the value of a if the value of 2x² + x - a equals to 5, when x = 0?
Answer:

= x = 0
= 2x² + x - a = 5
= a = 2x² + x - 5
a = (2 × 0²) + 0 - 5
a = 0 + 0 - 5
a = -5

Question 10: Simplify the expression and find its value when a = 5 and b = -3.
2(a² + ab) + 3 - ab
Answer:

= a = 5 and b = -3
= 2a² + 2ab + 3 - ab
= 2a² + ab + 3
= (2 × 5²) + (5 × (-3)) + 3
= (2 × 25) + (-15) + 3
= 50 - 15 + 3
= 53 - 15
= 38

No comments:

Post a Comment

Also read!

Click on any of the below text for additional links:

Class 6

Class 6 Computer Kips Solutions
Class 6 Gul Mohar English Solutions
→ Class 6 Map Pointing Solutions
Class 6 NCERT Civics Solutions
Class 6 NCERT Geography Solutions
Class 6 NCERT History Solutions
Class 6 NCERT Maths Solutions
Class 6 NCERT Science Solutions

Class 7

Class 7 Computer Kips Solutions
Class 7 Gul Mohar English Solutions
English Grammar Class 7
English Writing Skills Class 7
Class 7 Map Pointing Solutions
Class 7 NCERT Civics Solutions
Class 7 NCERT Civics Notes
Class 7 NCERT Civics Extra Questions
Class 7 NCERT Geography Solutions
Class 7 NCERT Geography Notes
Class 7 NCERT Geography Extra Questions
Class 7 NCERT History Solutions
Class 7 NCERT History Notes
Class 7 NCERT History Extra Questions
Class 7 NCERT Maths Solutions
Class 7 NCERT Science Solutions
Class 7 NCERT Science Notes
Class 7 NCERT Science Extra Questions

Class 8

Class 8 Kips Artificial Intelligence Solutions
Class 8 Gul Mohar English Solutions
English Grammar Class 8
English Writing Skills Class 8
Class 8 Map Pointing Solutions
Class 8 NCERT Civics Solutions
Class 8 NCERT Civics Notes
Class 8 NCERT Civics Extra Questions
Class 8 NCERT Geography Solutions
Class 8 NCERT Geography Notes
Class 8 NCERT Geography Extra Questions
Class 8 NCERT History Solutions
Class 8 NCERT History Notes
Class 8 NCERT History Extra Questions
Class 8 NCERT Maths Solutions
Class 8 NCERT Science Solutions
Class 8 NCERT Science Notes
Class 8 NCERT Science Extra Questions
Class 8 NCERT Science Exemplar
Class 8 NCERT Science MCQs

Class 9

Class 9 Kips Artificial Intelligence Solutions
Class 9 Map Pointing Solutions
Class 9 NCERT Civics Solutions
Class 9 NCERT Geography Solutions
Class 9 NCERT History Solutions
Class 9 NCERT Maths Solutions
Class 9 NCERT Science Solutions

Class 10

Class 10 Kips Artificial Intelligence Solutions
Class 10 NCERT English Solutions
→ Class 10 Map Pointing Solutions
Class 10 NCERT Civics Solutions
Class 10 NCERT Civics Notes
Class 10 NCERT Civics Extra Questions
Class 10 NCERT Geography Solutions
Class 10 NCERT Geography Notes
Class 10 NCERT Geography Extra Questions
Class 10 NCERT History Solutions
→ Class 10 NCERT History Notes
Class 10 NCERT History Extra Questions
Class 10 NCERT Maths Solutions
Class 10 NCERT Science Solutions
Class 10 NCERT Science Notes
Class 10 NCERT Science Extra Questions

Computer Languages

Python Basics

Extra Activities

Extra Activities

Extra Knowledge

Extra Information
General Knowledge
Historical Places in India
Latest technology
Physical Sciences
Facts

• Mathematics quick links
Mathematical Terms
Maths Tricks

Home Top