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Class 8 maths exercise 8.4 solutions

In this page we have Class 8 maths exercise 8.4 solutions for Algebraic Expressions .This exercise has questions about multiplication of polynomials by polynomials. Hope you like them and do not forget to like , social share and comment at the end of the page.

Class 8 maths exercise 8.4 solutions

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
Class 8 maths exercise 8.4 solutions

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 + a²x 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

Summary

Class 8 maths exercise 8.4 solutions has been prepared by Expert with utmost care. If you find any mistake.Please do provide feedback on mail. You can download the solutions as PDF in the below Link also
Download Algebraic Expressions Exercise 8.4 as pdf
This chapter 8 has total 4 Exercise 8.1 ,8.2 ,8.3 ,8.4 as per latest syllabus.Exercise 8.5 is deleted as per latest syllabus. This is the Fourth exercise in the chapter.You can explore previous exercise of this chapter by clicking the link below

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