solve by elimination

Question

{8x-3y=-11

{2x-5y=27

Answer 1

8x-3y=-11    ........... (1)
2x-5y=27    ............ (2)

 

The second equation should be multiplied by -4 and added to the first equation so that 8x gets eliminated. 

 

(1) + 4* (2) 

 

8x - 3y + -4(2x - 5y) = -11 + -4(27)

 

8x - 3y - 8x + 20y = -11 - 108

 

17y = 119

 

y = -7

 

Then substitute y = -7 to  equation (1)

 

8x - 3(-7) = -11

 

8x + 21  = -11

 

x = - 4 

 

Answer 2

multiply the second equation by 4:

8x-20y =108

use the first equation to substract this eauation:

-3y+20y = -11-108

17y =-119

y=-7

plug into the second equation:

2x+35=27

2x=-8

x=-4

so x=-4, y=-7