physicscatalyst.com logo





Ncert Solutions for Algebraic Expressions and Identities Class 8 Maths Chapter 9 Exercise 9.4





In this page we have NCERT Solutions for Algebraic Expressions and Identities Class 8 Mathematics Chapter 9 for Exercise 9.4 . Hope you like them and do not forget to like , social share and comment at the end of the page.
Question 1
 Multiply the binomials.
i) (2x + 5) and (4x – 3)
 (ii) (y – 8) and (3y – 4)
 (iii) (2.5l – 0.5m) and (2.5l + 0.5m)
 (iv) (a + 3b) and (x + 5)
 (v) (2pq + 3q2) and (3pq – 2q2)
Answer: Let  ( a+b) (c+d) to be done
then
( a+b) (c+d)= a(c+d) + b( c+d)
=a x  c+a x  d+b x  c+b x d
We will use the same concept in all the question below
i) (2x + 5)(4x - 3)
2x x 4x - 2x x 3 + 5 x 4x - 5 x 3
8x² - 6x + 20x -15
8x² + 14x -15
ii) ( y - 8)(3y - 4)
= y x 3y - 4y - 8 x 3y + 32
= 3y2 - 4y - 24y + 32
= 3y2 - 28y + 32
iii) (2.5l - 0.5m)(2.5l + 0.5)
Using (a+b)(a-b) = a2 - b2
We get = 6.25l2 - 0.25m2
iv) ax + 5a + 3bx + 15b
v) 2pq x 3pq - 2pq x 2q2 + 3q2 x 3pq - 3q2 x 2q2
= 6p2q2 - 4pq3 + 9pq3 - 6q4 = 6p2q2 - 5pq3 - 6p4
Question 2
Find the product.
(i) (5 – 2x) (3 + x)
 (ii) (x + 7y) (7x – y)
iii) (a2+ b) (a + b2)
 (iv) (p2– q2) (2p + q)
Answer: i) 15 + 5x - 6x - 2x2
= 15 - x - x 2
ii) 7x2 - xy + 49xy - 7y2
= 7x2 - 7y2 + 48xy
iii) a2 x a + ax b + a x b + b3
= a3 + a2b + ab + b3
= a3 + b3 + a2b + ab
iv) 2p3 + p2q - 2pq2 - q3
= 2p3 - q3 + p2q - 2pq2


Question 3
 Simplify.
(i) (x2– 5) (x + 5) + 25
 (ii) (a2+ 5) (b3+ 3) + 5
 (iii) (a + b) (c – d) + (a – b) (c + d) + 2 (ac + bd)
 (iv) (x + y)(2x + y) + (x + 2y)(x – y)
 (v) (x + y)(x2– xy + y2)
 (vi) (1.5x – 4y)(1.5x + 4y + 3) – 4.5x + 12y
 (vii) (a + b + c)(a + b – c)
Answer:
i) x3 + 5x2 - 5x - 25 + 25
= x3 + 5x2 -5x
ii) a2b3 + 3a2 + 5b3 + 15 + 5
= a2b3 + 5b3 + 3a2 + 20
iii) (ac - ad + bc - bd) + (ac + ad - bc - bd) + (2ac + 2bd)
= ac - ad + bc - bd + ac + ad - bc - bd + 2ac + 2bd
= 4ac
iv) 2x2 + xy + 2xy + y2 + x2 - xy + 2xy - 2y2
= 3x2 + 4xy - y2
v) x3 - x2y + xy2 + x2y - xy2 + y3
= x3 + y3
vi) 2.25x2 + 6xy + 4.5x - 6xy - 16y2 - 12y - 4.5x + 12y
= 2.25x2 - 16y2
vii) a2 + ab - ac + ab + b2 - bc + ac + bc - c2
= a2 + b2 - c2 + 2ab

Download Algebraic Expressions Exercise 9.4 as pdf
link to this page by copying the following text


Class 8 Maths Class 8 Science
Reference Books for class 8 Math

Given below are the links of some of the reference books for class 8 Math.

  1. Mathematics Foundation Course for JEE/Olympiad : Class 8 This book can take students maths skills further. Only buy if child is interested in Olympiad/JEE foundation courses.
  2. Mathematics for Class 8 by R S Aggarwal Detailed Mathematics book to clear basics and concepts. I would say it is a must have book for class 8 student.
  3. Pearson Foundation Series (IIT -JEE / NEET) Physics, Chemistry, Maths & Biology for Class 8 (Main Books) | PCMB Combo : These set of books could help your child if he aims to get extra knowledge of science and maths. These would be helpful if child wants to prepare for competitive exams like JEE/NEET. Only buy if you can provide help to the child while studying.
  4. Reasoning Olympiad Workbook - Class 8 :- Reasoning helps sharpen the mind of child. I would recommend students practicing reasoning even though they are not appearing for Olympiad.

You can use above books for extra knowledge and practicing different questions.







Note to our visitors :-

Thanks for visiting our website. From feedback of our visitors we came to know that sometimes you are not able to see the answers given under "Answers" tab below questions. This might happen sometimes as we use javascript there. So you can view answers where they are available by reloding the page and letting it reload properly by waiting few more seconds before clicking the button.
We really do hope that this resolve the issue. If you still hare facing problems then feel free to contact us using feedback button or contact us directly by sending is an email at [email protected]
We are aware that our users want answers to all the questions in the website. Since ours is more or less a one man army we are working towards providing answers to questions available at our website.