Solve the following pair of equations by drawing graphs:-

   x + y = 6

   x  - y = -4

  

    Solution

1.  Re-arrange equations into form y = mx + c

              y = 6 - x

              y = x + 4

 

2.  Take first equation.             

Pick 3 sensible points for x, then solve for y.

 

 

 

y = 6 - x	x	-2	0	6
	y	8	6	0

 

 

Plot points on grid.  {Co-ords ( -2,8), (0,6) , (6, 0)}

Join with straight line.

 

3.  Repeat for other equation.

 

y = x + 4	x	-4	0	4
	y	0	4	8

 

      Plot Co-ords ( -4,0), (0,4) , (4, 8)  and join with straight line.

 

 

        

 

 

4.  Read off intersection. ( 1,5)

         so  x = 1,  y = 5

            Check  

             x + y = 6,so 1+5 = 6    

               x-y = - 4, 1-5 = - 4  

 

5.  Write out solution    

The solution is the point of intersection  ( 1, 5)

 x = 1,  y = 5