Question

Solve the system of equations algebraically by using substitution method:

-3x+3y=9
-x+y=3

Answer 1

This system has infinite solutions and it would be much easier to solve it by elimination but substitution it is.

Explanation:

-3x+3y=9

-x+y=3

Isolate either x or y in any of the equations. I'll go with the second.

y = 3+x

Now substitute this for y in the first equation.

-3x+3(3+x)=9

Distribute the 3

-3x+9+3x=9

Combine like terms:

9=9

0=0

It's infinite