Question

−4x + y = 6
−5x − y = 21

Answer 1

assuming x=x and  y=y in both equations
add them together

-4x+y=6
-5x-y=21  +
-9x+0y=27
-9x=27
divide by 9
-x=3
multiply -1
x=-3

subsiutte
-4x+y=6
-4(-3)+y=6
12+y=6
subtract 12
y=-6



x=-3
y=-6
the soultion set is in (x,y) form
(-3,-6)