Question

Find the solution to the system of equations below (you can do this by substitution or elimination).

-4x+y=6
-5x-y=21

Answer 1

Explanation:

y=6+4x, as equation (iii)

=> -5x-(6+4x)=21

=> -5x-6-4x=21

=> -5x-4x-6=21

=> -9x-6=21

=> -9x=21+6

=> -9x=27

x= -3, by dividing both sides by -9

So, by inserting x in the first equation,

=> -4(-3)+y=6

=> 12+y=6

=> y=6-12

=> y= -6.

Therefore, x= -3 and y= -6