Request a call back

Join NOW to get access to exclusive study material for best results

Class 9 NCERT Solutions Maths Chapter 4 - Linear Equations in Two Variables

Linear Equations in Two Variables Exercise Ex. 4.1

Solution 1

Let cost of notebook and a pen be x and y respectively.
Cost of note book = 2  cost of pen  
              x = 2y
      x - 2 y = 0

Solution 2

(i)

     Comparing this equation with ax + by + c = 0
     
(ii)

       Comparing this equation with ax + by + c = 0
 
       a = 1, b = - , c = -10
(iii)  - 2x + 3 y = 6  
       - 2x + 3 y - 6 = 0
       Comparing this equation with ax + by + c = 0
       a = - 2, b = 3, c = -  6   
 
(iv)  x = 3y
       1x - 3y + 0 = 0  
       Comparing this equation with ax + by + c = 0
       a = 1, b = - 3, c = 0
 
(v)  2x = - 5y
      2x + 5y + 0 = 0  
      Comparing this equation with ax + by + c = 0
      a = 2, b = 5, c = 0
 
(vi)  3x + 2 = 0
       3x + 0.y + 2 = 0
        Comparing this equation with ax + by + c = 0
        a = 3, b = 0, c = 2
(vii)  y - 2 = 0  
        0.x + 1.y - 2 = 0  
        Comparing this equation with ax + by + c = 0
        a = 0, b = 1, c = - 2
 
(viii)  5 = 2x
         - 2x + 0.y + 5 = 0
        Company this equation with ax + by + c = 0
        a = - 2, b = 0, c = 5

       



   

Linear Equations in Two Variables Exercise Ex. 4.2

Solution 1

y = 3x + 5 is a linear equation in two variables and it has infinite solutions. As for every value of x there will be a value of y satisfying above equation and vice versa.
Hence, the correct answer is (iii).

Solution 2

(i)    2x + y = 7
         For x = 0
    2(0) + y = 7
        y = 7
    So, (0, 7) is a solution of this equation
        For x = 1
    2(1) + y = 7
          y = 5
    So, (1, 5) is a solution of this equation
 
            For x = -1
     2(-1) + y = 7
              y = 5
      So, (-1, 9) is a solution of this equation
            For x = 2
       2(2) + y = 7
             y = 3
       So (2, 3) is a solution of this equation.
 
(ii)    + y = 9
             For x = 0
      (o) + y = 9
              y = 9
      So (0, 9) is a solution of this equation
      For x = 1
      (1) + y =9
      y = 9 -
      So, (1, 9 - ) is a solution of this equation 
      For x = 2
      (2) + y = 9
      y = 9 - 2
       So, (2, 9 -2) is a solution of this equation
       For x = -1
        (-1) + y = 9
                     y = 9 +
        So, (-1, 9 + ) is a solution of this equation 
(iii)   x = 4y    
        For x = 0
        0 = 4y
        y = 0
        So, (0, 0) is a solution of this equation  
        For y = 1
        x = 4(1) = 4
        So, (4, 1) is a solution of this equation
        For y = - 1
        x = 4(-1)
        x = -4
        So, (-4, - 1) is a solution of this equation
        For x = 2
        2 = 4y
        y =
        So, 
is a solution of this equation.
 
 

Solution 3

(i)   (0, 2)
      Putting x = 0, and y = 2 in the L.H.S of given equation
      x - 2y = 0 - (22 )
               = - 4
      As -4 # 4   
      L.H.S # R.H.S
      So (0, 2) is not a solution of this equation.
 
(ii)  (2, 0)
      Putting x = 2, and y = 0 in the L.H.S of given equation
      x - 2y = 2 - (2  0)
              = 2 
              As 2 # 4
      L.H.S  R.H.S
      So (2, 0) is not a solution of this equation.
 
(iii)  (4, 0)
       Putting x = 4, and y = 0 in the L.H.S of given equation
       x - 2y  = 4 - 2(0)
       = 4 = R.H.S
       So (4, 0) is a solution of this equation.
 
(iv)   
       Putting x =  and y = 4 in the L.H.S of given equation.

         
                        
      L.H.S  R.H.S
      So   is not a solution of this equation.  
(v)  (1, 1)
      Putting x = 1, and y = 1 in the L.H.S of given equation
      x - 2y  = 1 - 2(1)
                = 1 - 2
                = - 1 
               As -1 # 4
                       L.H.S  R.H.S
      So (1, 1) is not a solution of this equation.

Solution 4

Putting x = 2, and y = 1 in the given equation
2x + 3y = k  
2(2) + 3(1) = k
4 + 3 = k
      k = 7

Get Latest Study Material for Academic year 24-25 Click here
×