Linear Equations with two variable(4)

Example 1:

   Solve the following equations

  x+ y = 7 , 

    x = 4

the answer :

Put value of x  in the first equation to get value of y

4      + y = 7

       y = 7- 4 = 3

the solution to this equations = {(4, 3)}

Example 2:

   Solve the following equations

  x+ y = 6 ,  

    y = 2

the answer :

Put value of y  in the first equation to get value of x

          x+ 2 = 6      

        x = 6- 2 = 4

the solution to this equations = {(4, 2)}

Example 3:

   Solve the following equations

 3 x+ y = 11 , 

    x = 4

the answer :

Put value of x  in the first equation to get value of y

3 ×4  +  y = 11

       y = 11- 12 = -1

the solution to this equations = {(4, -1)}

Example 4:

   Solve the following equations

   x+ y = 3   

   x  + y = 7

the answer   

 x+ y = 3  …… ×- 1   

x  + y = 7 ……… ×1

x- y =- 3     -

  x  + y = 7

    0 = 4   ???? !!!!!

the solution to this equations = Ø

Example 5:

   Solve the following equations

   x- 2 y = 8   

   x  - 2 y = 3

the answer : 

x- 2 y = 8  …… ×- 1  

  x  -2 y = 3 ….… ×1

 - x+ 2 y =- 8      

    x  -2 y = 3  

   0   =    - 5   ????? !!!!!!

the solution to this equations = Ø