Homework Help: Algebra

Posted by Max on Saturday, November 13, 2010 at 8:06pm.

Solving systems of linear equations in 3 variables...

1) 3x-2y+2z=1
2) 2x+5y-5z=7
3) 4x-3y+z=-3

I combined 1 and 3 to get -5x+4y=7
And then i combined 2 and 3 to get
-13y+11z=-17. Can that be right? how would you combine those two equations?

Algebra - bobpursley, Saturday, November 13, 2010 at 8:09pm
you should when combining 2 and 3, multiply to get rid of z, so multiply 3 by 5, then add.
Algebra - Reiny, Saturday, November 13, 2010 at 8:13pm
You would like to have the same two variables in the two new equations.
Your first one contains x and y, but your second contains y and z. This gets you nowhere.

Your first equation is ok,
Now take 5 times the third and add it to the second.
Algebra - Max, Saturday, November 13, 2010 at 8:16pm
So you would get 22x-10y=-8? how would you combine that with -5x+4y=7?
Algebra - Max, Saturday, November 13, 2010 at 8:20pm
THanks guys! i get it now!

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