Question

What is the solution to the system of equations? Use the substitution method to solve.

6=−4x+y
−5x−y=21

Please help! And, if you don't mind, could you explain to me what the substitution method is? Thanks guys!

Answer 1

In the substitution method, you will take the value of one variable in one equation and replace the variable in the second equation with that value.
For instance
6=-4x+y
6+4x=-4x+y+4x So the value of y is 6+4x
6+4x=y y=6+4x
In the second equation, replace every y with 6+4x
-5x-y=21 -9x-6+6=21+6 x=-3
-5x-(6+4x)=21 -9x=27 So using the value of y, we found -5x-6-4x=21 -9x/-9=27/-9 the value of x

y=6+4(-3) y=6-12 y=-6 Using substitution, we know that x=-3 and y=-6