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⇱ Class 8 NCERT Solutions- Chapter 14 Factorisation - Exercise 14.4 - GeeksforGeeks


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Class 8 NCERT Solutions- Chapter 14 Factorisation - Exercise 14.4

Last Updated : 23 Sep, 2024

Exercise 14.3 of Chapter 14 (Factorisation) in the Class 8 NCERT Mathematics textbook focuses on factoring algebraic expressions using various methods.

This exercise helps students understand how to break down complex expressions into simpler factors, which is a crucial skill in algebra.

Find and correct the errors in the following mathematical statements:

Question 1. 4(x - 5) = 4x - 5

Solution:

Given: 4(x - 5) = 4x - 5

Now we check if the given statement is correct or not

Taking L.H.S:

= 4(x - 5)

= 4x - 20

L.H.S ≠ R.H.S

So, the correct solution of 4(x - 5) = 4x - 20

Question 2. x(3x + 2) = 3x2+ 2

Solution:

Given: x(3x + 2) = 3x2+ 2

Now we check if the given statement is correct or not

Taking L.H.S:

= x(3x + 2)

= 3x2 + 2x

L.H.S ≠ R.H.S

So, the correct solution of x(3x + 2) = 3x2+ 2x

Question 3. 2x + 3y = 5xy

Solution:

Given: 2x + 3y = 5xy

Here, L.H.S ≠ R.H.S

So, the correct solution of 2x + 3y = 2x + 3y

Question 4. x + 2x + 3x = 5x 

Solution:

Given: x + 2x + 3x = 5x 

Now we check if the given statement is correct or not

Taking L.H.S:

= x + 2x + 3x

= 6x

L.H.S ≠ R.H.S

So, the correct solution of x + 2x + 3x = 6x

Question 5. 5y + 2y + y – 7y = 0 

Solution:

Given: 5y + 2y + y – 7y = 0 

Now we check if the given statement is correct or not

Taking L.H.S:

= 5y + 2y + y – 7y 

= y

L.H.S ≠ R.H.S

So, the correct solution of 5y + 2y + y – 7y = y

Question 6. 3x + 2x = 5x2

Solution:

Given: 3x + 2x = 5x2

Now we check if the given statement is correct or not

Taking L.H.S:

= 3x + 2x

= 5x

L.H.S ≠ R.H.S

So, the correct solution of 3x + 2x = 5x

Question 7. (2x)2+ 4(2x) + 7 = 2x2+ 8x + 7 

Solution:

Given: (2x)2+ 4(2x) + 7 = 2x2+ 8x + 7 

Now we check if the given statement is correct or not

Taking L.H.S:

= (2x)2+ 4(2x) + 7

= 4x2 + 8x + 7

L.H.S ≠ R.H.S

So, the correct solution of (2x)2+ 4(2x) + 7 = 4x2 + 8x + 7

Question 8. (2x)2+ 5x = 4x + 5x = 9x

Solution:

Given: (2x)2+ 5x = 4x + 5x = 9x

Here, 

4x + 5x ≠ 9x

So, we check (2x)2+ 5x = 4x + 5x or not

Taking L.H.S:

= (2x)2+ 5x

= 4x2 + 5x 

L.H.S ≠ R.H.S

So, the correct solution of (2x)2+ 5x = 4x2 + 5x 

Question 9. (3x + 2)2= 3x2+ 6x + 4 

Solution:

Given: (3x + 2)2= 3x2+ 6x + 4 

Now we check if the given statement is correct or not

Taking L.H.S:

= (3x + 2)2

= 9x2 + 6x + 4

L.H.S ≠ R.H.S

So, the correct solution of (3x + 2)2 = 9x2 + 6x + 4

Question 10. Substituting x = - 3 in

(a) x2+ 5x + 4 gives (– 3)2 + 5 (-3) + 4 = 9 + 2 + 4 = 15

Solution:

Given: x2+ 5x + 4

Now substitute the value of x = -3 in the given equation, 

= (-3)2+ 5(-3) + 4

= 9 - 15 + 4

= -2

So the correct solution of x2+ 5x + 4 = -2

(b) x2 - 5x + 4 gives (- 3)2 - 5 ( - 3) + 4 = 9 - 15 + 4 = – 2

Solution:

Given: x2 - 5x + 4

Now substitute the value of x = -3 in the given equation, 

= (-3)2 - 5(-3) + 4

= 9 + 15 + 4

= 28

So the correct solution of x2 - 5x + 4 = 28

(c) x2+ 5x gives (- 3)2+ 5 (-3) = - 9 - 15 = - 24

Solution:

Given: x2 + 5x 

Now substitute the value of x = -3 in the given equation, 

= (-3)2 + 5(-3) 

= 9 - 15 

= -6

So the correct solution of x2 + 5x = -6

Question 11. (y - 3)2 = y2 - 9 

Solution:

Given: (y - 3)2 = y2 - 9 

Now we check if the given statement is correct or not

Taking L.H.S:

= (y - 3)2

= y2 - 6y + 9

L.H.S ≠ R.H.S

So, the correct solution of (y - 3)2 = y2 - 6y + 9

Question 12. (z + 5)2 = z2 + 25

Solution:

Given: (z + 5)2 = z2+ 25

Now we check if the given statement is correct or not

Taking L.H.S:

= (z + 5)2

= z2 + 10z + 25

L.H.S ≠ R.H.S

So, the correct solution of (z + 5)2 = z2 + 10z + 25

Question 13. (2a + 3b) (a - b) = 2a2 - 3b2

Solution:

Given: (2a + 3b) (a - b) = 2a2 - 3b2

Now we check if the given statement is correct or not

Taking L.H.S:

= (2a + 3b) (a - b) 

= 2a2 - 2ab + 3ab - 3b

= 2a2 - 3b2 + ab 

L.H.S ≠ R.H.S

So, the correct solution of (2a + 3b) (a - b) = 2a2 - 3b2 + ab 

Question 14. (a + 4) (a + 2) = a2 + 8

Solution:

Given: (a + 4) (a + 2) = a2 + 8

Now we check if the given statement is correct or not

Taking L.H.S:

= (a + 4) (a + 2)

= a2 + 2a + 4a + 8

= a2 + 6a + 8

L.H.S ≠ R.H.S

So, the correct solution of (a + 4) (a + 2) = a2 + 6a + 8

Question 15. (a - 4) (a - 2) = a2 - 8

Solution:

Given: (a - 4) (a - 2) = a2 - 8

Now we check if the given statement is correct or not

Taking L.H.S:

= (a - 4) (a - 2)

= a2 - 2a - 4a + 8

= a2 - 6a + 8

L.H.S ≠ R.H.S

So, the correct solution of (a - 4) (a - 2) = a2 - 6a + 8

Question 16. 3x2/3x2 = 0

Solution:

Given: 3x2/3x2 = 0

Now we check if the given statement is correct or not

Taking L.H.S:

= 3x2/3x2

= 1

L.H.S ≠ R.H.S

So, the correct solution of 3x2/3x2 = 1

Question 17. (3x2 + 1)/(3x2) = 1 + 1 = 2

Solution:

Given: (3x2 + 1)/(3x2) = 1 + 1 = 2

Now we check if the given statement is correct or not

Taking L.H.S:

= (3x2 + 1)/(3x2)

= 3x2/(3x2)+ 1/(3x2)

= 1 + 1/(3x2)

L.H.S ≠ R.H.S

So, the correct solution of (3x2 + 1)/(3x2) = 1 + 1/(3x2)

Question 18. (3x)/(3x + 2) = 1/2

Solution:

Given: (3x)/(3x + 2) = 1/2

Here, L.H.S ≠ R.H.S

So, the correct solution of (3x)/(3x + 2) = (3x)/(3x + 2)

Question 19. 3/(4x + 3) = 1/4x

Solution:

Given: 3/(4x + 3) = 1/4x

Here, L.H.S ≠ R.H.S

So, the correct solution of 3/(4x + 3) = 3/(4x + 3) 

Question 20. (4x + 5)/(4x) = 5

Solution:

Given: (4x + 5)/(4x) = 5

Now we check if the given statement is correct or not

Taking L.H.S:

= (4x + 5)/(4x) 

= (4x/4x) + 5/4x)

= 1 + 5/4x

L.H.S ≠ R.H.S

So, the correct solution of (4x + 5)/(4x) = 1 + 5/4x

Question 21. (7x + 5)/5 = 7x

Solution:

Given: (7x + 5)/5 = 7x

Now we check if the given statement is correct or not

Taking L.H.S:

= (7x + 5)/5

= (7x/5) + 5/5)

= 7x/5 + 1

L.H.S ≠ R.H.S

So, the correct solution of (7x + 5)/5 = 7x/5 + 1

Summary

Exercise 14.4 of Chapter 14 on Factorisation introduces students to the crucial algebraic skill of division. This exercise builds upon previously learned factorization techniques and extends them to the realm of dividing polynomials by monomials and binomials. Through a series of carefully crafted problems, students learn to apply the distributive property, identify common factors, and use long division for more complex polynomial divisions. The problems range from simple divisions of monomials to more challenging divisions of quadratic expressions by linear factors. This exercise not only reinforces students' understanding of algebraic manipulation but also prepares them for more advanced topics in algebra, such as polynomial long division, synthetic division, and the factor theorem. Mastery of these division techniques is essential for simplifying rational expressions, solving higher-degree equations, and understanding the behavior of polynomial functions in higher mathematics. By working through these problems, students develop their analytical thinking, pattern recognition, and problem-solving skills, all of which are fundamental to success in mathematics and related fields.`

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