Quick question regarding solving a system by substitution

[travispastrana<3]

When you are solving a system using substitution

Ex.
x - 3y + 6z = 21
3x + 2y - 5z = -30
2x - 5y + 2z = -6

And you make the 'x = ' would the 21 become negative?

Like: x = -3y + 6z + 21 or maybe -21 ???

 

[Ted]

Well it would still be 21. The idea is that you have to do the same thing to each side of the equals sign.

In order to get X by itself, what can you do?

1) Add 3y to each side

2) Subtract 6z from each side

3) Simplify: x = 21 + 3y - 6z

See how I did that one? When a term moves to the other side of the equals sign, it switches from positive to negative.

Ted

 

[travispastrana<3]

Oh, ok I get it now.
Thanks a bunch :]]