Solve system by using addition method

Question

2x+5y=9

4x-7y=-16

Answer 1

Hi ,

 

Given equations are : 2x+5y = 9      ,    4x+7y = 16

 

Multiplying first equation by 2, we get

 

4x+10y = 18

 

Subtract 4x+7y = 16 from this

 

     4x   +   10y   =   18

  -_4x_+__7y___=__16___

 

                3y     =     2

 

y=2/3, Substitute this value in first equation

 

2x  +  5 (2/3)  =  9

 

2x   = 9  -  10/3

 

2x   =  (27-10) / 3

 

2x  =  17/3         , therefore  x  =  17/6    and   y = 2/3