10th cbse maths solution for exercise 4.2 part 1

This page 10th cbse maths solution for exercise 4.2 part 1is going to provide you solution for every problems that you find in the exercise no 4.2

10th CBSE maths solution for Exercise 4.2 part 1

(ii) 2 x² + x - 6 = 0

Solution:

2 x² + 4 x - 3 x - 6 = 0

2 x (x + 2) - 3 (x + 2) = 0

(2 x - 3) (x + 2) = 0

  2 x - 3 = 0     x + 2 = 0

   2 x = 3          x = -2

     x = 3/2

Therefore the roots are 3/2 and -2.


(iii) √2 x² + 7 x + 5 √2 = 0

Solution:

√2 x² + 7 x + 5 √2 = 0

√2 x² + 5 x + 2 x + 5 √2 = 0

√2 x² + 5 x + √2 √2 x + 5 √2 = 0

x (√2 x + 5) + √2 (√2 x + 5) = 0

(√2 x + 5) (x + √2) = 0

  √2 x + 5 = 0     x + √2 = 0

   √2 x = -5          x = -√2

     x = -5/√2

Therefore the roots are -5/√2 and -√2.


(iv) 2 x² - x + (1/8) = 0

Solution:

16 x²- 8 x + 1 = 0

16 x²- 4 x - 4 x + 1 = 0

4 x (4 x - 1) - 1 (4 x - 1) = 0

(4 x - 1) (4 x - 1) =0

 4 x - 1 = 0     4 x - 1 = 0

   4 x = 1 

     x = 1/4

Therefore the roots are 1/4 and 1/4.


(v) 100 x² - 20 x + 1 = 0

Solution:

100 x² - 20 x + 1 = 0

100 x² - 10 x - 10 x + 1 = 0

10 x (10 x - 1) - 1 (10 x - 1) = 0

(10 x - 1) (10 x - 1) = 0

 10 x - 1 = 0

   10 x = 1 

     x = 1/10

Therefore the roots are 1/10 and 1/10.


(i) John and Jivanti together have 45 marbles. Both of them lost 5 marbles each, and the product of the number of marbles they have now is 124. We would like to find out how many marbles they had to start with.

Solution:

Let 'x' be the number of marbles that john has

Let '45 - x' be the number of marbles that Jivanthi has

After losing 5 marbles

Number of marbles with John = x - 5

Number of marbles with Jivanti = 45 - x - 5

                                               = 40 - x

The product of number of marbles = 124

                            (x - 5) (40 - x) = 124

                       40 x - x²- 200 + 5 x = 124

                       45 x - x²- 200 = 124

                x²- 45 x + 124 + 200 = 0

                x²- 45 x + 324 = 0

                x²- 36 x - 9 x + 324 = 0

                x (x - 36) - 9 (x - 36) = 0

               (x - 9) (x - 36) = 0

   x - 9 = 0            x - 36 = 0

        x = 9              x = 36

So John is having 36 marbles,when Jivanti is having 9 marbles or Jivanti is having 36 marbles,when John is having 9 marbles.  10th cbse maths solution for exercise 4.2 part 1
10th cbse maths solution for exercise 4.2 part 1




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