Linear Equations with two variable(1)

 the method of elimination""

Example 1: 

 Solve the following equations 

   ,  x+ y = 5   x – y = 1

the answer :

x+ y = 5

x – y = 1 

2 x = 6

X=6 /2 

X =3

Put value of x  in

  the first equation   

x+ y= 5

3 + y = 5

Y =5 – 3

Y = 2

the solution to this equations = {(3 , 2)}

 Example 2:

Solve the following equations

 ,  x+ y = 9  x – y = 3

the same ……….

the solution to this equations = {(6, 3)}

 

 Example 3:Solve the following equations

   ,  x+ y = 4  x – y = 2

the same ……….

the solution to this equations = {(3,1)} 

 

   Example 4:

 Two numbers equal to 12 ,

The difference between them is 6

 Find the two numbers 

the answer :

let the two numbers is  X  and y

then : x + y =12  , x – y = 6

the same……….

The two numbers is 9 , 3

Example 5 :

 two supplementary angles ,  

The difference between them is 20 degrees

 Find the  measurement of each angle

the answer :

 of the two angles  is  X  and y  measurement let the 

then :   x + y =180   , x – y = 20

the same……….

      the two angles  is  100  and 80