Question

solve -4x-6y=68, x+2y=-21by using substitution. Express your answer as an ordered pair

Answer 1

Solve one of the equations for x or y. Plug it back into the same equation or the other one.

Answer 2

I always preferred adding the equations.

\[4*(eq_2) + eq_1 \rightarrow 2y = 68-84\ ...\ etc\]

Answer 3

ok so what we can do here is the following:

with equation x + 2y = -21
will become x = - 21 - 2y

so from here we can substituate x into the first equation.

-4x-6y=68
so -4(-21-2y)-6y = 68
84 + 8y - 6y = 68
2y = -16
so y = -8.

so in this case x = -21 - 2(-8)
x = -21 + 16 = 5

so x = 5 and y = -8 is the solution to the two equations