Question

Solve the following pair of equation

1/3x + y + 1/3x - y = 3/4 , 1/2(3x + y) - 1/2(x-y) = -1/8


CLASS 10TH CBSE SAMPLE PAPER 2018-19

Answer 1

First plz see. The pic Adding equation( 3) and (4) 3x-y=2 3x+y=4 =>6x=6 =>x=1 now put in the (3) equation 3*1-y=2 Y=1 and x=1 Hope its help you dude Thanks

Answer 2

Hi !


$\frac{1}{3x + y} + \frac{1}{3x - y} = \frac{3}{4}$

Let 1/3x + y = a , and 1/3x - y = b ,

a + b = 3/4       -----------------> (1)

4a + 4b = 3                   -------------> (1)

also ,

$\frac{1}{2 ( 3x + y)} - \frac{1}{2(3x - y)} = -1/8$

a/2 - b/2 = -1/8

(a - b)/2 = -1/8

a - b = -1/4

4a - 4b = -1                   ---------------------------> (2)

Adding equations (1) and (2) :-

4a + 4b = 3

4a - 4b = -1
--------------------

8a = 2

a = 2/8

a = 1/4

4a - 4b = -1

4*1/4 - 4b = -1

1 - 4b = -1

4b = 1 + 1

4b = 2

b = 2/4

b = 1/2

1/3x + y = a 

1/3x + y = 1/4

3x + y = 4         -----------------> (3)

1/3x - y = b

1/3x - y = 1/2

3x - y = 2                 -----------------> (2)

Adding equations (3) and (4) :-

3x + y = 4
3x - y = 2
--------------------------

6x = 6

x = 1

3x + y = 4
3*1 + y = 4

y = 4 - 3 = 1

Hence,

x = 1 , y = 1