How do you solve #x= -2y+10# and #3x-y=9# using substitution?
When solving systems of equations using the substitution method, the whole goal is to plug one equation into the other to find solutions for variables.
To do this, you want at least one of your equations in the system to be isolated for a variable. For example, compare your first and your second equations. Your first equation,
To begin, take your equation that has a variable isolated by itself in it (in your case,
This means that for any equations in your system, you can substitute (
So, let's substitute (
Distribute the 3, combine like terms, and solve for the variable.
This gives you the answer to one of your variables. Now that you have a new expression with an isolated variable, you can substitute it back into either of your original equations to solve for the other unsolved variable.
Plug the answer you got (
You can check that the answers you got (
Plug 4 in for
Thus, we know that our answers are correct because we got a true statement in return. Hope this helps!