Desperate need of Algebra 2 help

[Alysser]

I seriously don't get anything I am learning right now. I paid attention to the notes, but honestly, I just don't even get where to start. We are learning

SOLVING LINEAR SYSTEMS WITH THREE VARIABLES. DOES anyone KNOW how do this? It's for extra credit, which I need so desperately I have been trying to understand this for an hour with videos one youtube and it's not working at all :/ I am going to try again. If someone could teach me with one problem clearly I can probably get it. Here's a problem

8x + 2y - Z = -25
3x - 3y + 5z = 10
-5x + 6y - 2z = 17


If no one gets it I understand, Cause I certainly don't but this is worth a try posting. Thanks in advance.

[caseysmom]

My kid will know, when she gets home (from math tutoring) in an hour I will have her help you if nobody else has. I can even have her call you if necessary...you are siblings you know

[Daisy and Delilah]

Please post the answer. I am so rusty on this but I have a guess. I can't wait.

[Alysser]

I still haven't found it, I gave up on them, I can't get it AT ALL. My friend is helping me with them tomorrow morning hopefully. Hehe, thanks mom! Always trying to help - It'd be great if my "sister" could help me out.

[caseysmom]

My daughter started replying and then she got frustrated, she hasn't had algebra 2 since she was a freshman so she is rusty also.

She may come back and finish her reply later..

[Alysser]

My daughter started replying and then she got frustrated, she hasn't had algebra 2 since she was a freshman so she is rusty also.

She may come back and finish her reply later..

Tell her thank you for me! Thanks for trying to help, because I don't even get it at all. I appreciate any effort. I am a junior in Algebra 2, shows how smart I am

[caseysmom]

Well it must be hard because she is a math wiz...she drafted an answer but she isn't sure its rights...i'm tempted to send it behind her back

[Riptide]

Maybe this will help?

http://www.coolschool.ca/lor/PMA11/unit5/U05L06.htm

[smokey the elder]

I tried solving it as a matrix but linear algebra was over 30(!) years ago and I stunk on ice at it then! Good luck.

[emily_the_spoiled]

If I remember correctly it is something like this...

1) equation 1 (8x + 2y - Z = -25 ) solve for X (you will end up with a Y and a Z in the answer))

2) substitute the answer from step 1 into equation 2 (3x - 3y + 5z = 10) and solve for Z (you will end up with a Y in the answer but no X)

3) substitute the Z answer from the previous steps into equation 3 (-5x + 6y - 2z = 17) and solve for Y ( you will end up with an X in the answer but no Z)

4) substitute the answer from step 2 and 3 in to equation 1, solving for X. This time you will get a numerical answer. Then you can solve for the remaining variables based on the answers from step 2 and 3.

Good luck!

[Barbara]

8x + 2y - Z = -25
3x - 3y + 5z = 10
-5x + 6y - 2z = 17

Take the first equation and multiply it by 5:
5*(8x + 2y -z)= 5*(-25)
40x + 10y-5z=-125
Then add it to equation #2
40x +3x +10y-3y-5z+5z= -125+10
43 x +7y= -115

Then take the first equation and multiply it by -2
-2*(8x +2y -z)= -2*(-25)
-16x -4y +2z =50

Add it to equation #3
-16x -5x -4y +6y +2z -2z=17+50
-21x +2y= 67

Now you have two equations left with only x and y:
43x + 7y =-115
-21 x +2y=67

From the second equation you get
2y=21x+67

y= (21x +67)/2 ((We call this equation A as I'll need it in a second))

Put this in the first equation

43x + 7/2(21x+67)=-115

43x +7*21x/2 +7*67/2=-115


I hope you are better in calculating these numbers than I am because while I can do the math I make plenty of faults when calculating numbers. When in school I always got results like that - e.g. I can see that 7*21/2 will by no means be a nice number like 4 or even 15. So I hope I get the numbers right

43x + 73,5x +234,5 =-115
116,5 x =-349,5
x=-349,5/116,5
x=-3

Now we go back to equation A:
y=(21x +67)/2
y=(21*(-3)+67)/2
y=(-63+67)/2
y=4/2
y=2


Now we could go back to any of the first equations but I suppose #1 will be easiest.
8x + 2y - Z = -25
You bring the z to one side:
z=8x+2y+25
z=8*(-3)+2*2+25
z=-24+4+25
z=5

I suppose it is right as all the results are nice and clean

That was fun. Math for me is also 30 years ago but it was my favorite

[lvpets2002]

Good Luck Kidos.. Hey I stunk at it then & know I am plum dumb with it now.. I have been out of school for over 33 years.. However reading your post are making my head spin..

[Alysser]

THANK you guys so much for your help!! SOO much, I kinda get this a little better now THANK YOU! Barbara, thanks so much for the step by step info and showing the work. This is exactly what I needed Thanks so much, you guys are the best

[lizbud]

Take the first equation and multiply it by 5:
5*(8x + 2y -z)= 5*(-25)
40x + 10y-5z=-125
Then add it to equation #2
40x +3x +10y-3y-5z+5z= -125+10
43 x +7y= -115

Then take the first equation and multiply it by -2
-2*(8x +2y -z)= -2*(-25)
-16x -4y +2z =50

Add it to equation #3
-16x -5x -4y +6y +2z -2z=17+50
-21x +2y= 67

Now you have two equations left with only x and y:
43x + 7y =-115
-21 x +2y=67

From the second equation you get
2y=21x+67

y= (21x +67)/2 ((We call this equation A as I'll need it in a second))

Put this in the first equation

43x + 7/2(21x+67)=-115

43x +7*21x/2 +7*67/2=-115


I hope you are better in calculating these numbers than I am because while I can do the math I make plenty of faults when calculating numbers. When in school I always got results like that - e.g. I can see that 7*21/2 will by no means be a nice number like 4 or even 15. So I hope I get the numbers right

43x + 73,5x +234,5 =-115
116,5 x =-349,5
x=-349,5/116,5
x=-3

Now we go back to equation A:
y=(21x +67)/2
y=(21*(-3)+67)/2
y=(-63+67)/2
y=4/2
y=2


Now we could go back to any of the first equations but I suppose #1 will be easiest.
8x + 2y - Z = -25
You bring the z to one side:
z=8x+2y+25
z=8*(-3)+2*2+25
z=-24+4+25
z=5

I suppose it is right as all the results are nice and clean

That was fun. Math for me is also 30 years ago but it was my favorite

Wow, Barbara, color me impressed. Math was never my strong suit.

[RICHARD]

That is the thing that rocks about PT.

I started to look at Barbara's work then said some dirty words......
Who cares about the answers!


I want to know how long she took to type it all out!

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I just finished watching a documentary about the IMO of 2006.

http://www.unl.edu/amc/e-exams/e9-im...pictures.shtml

I think I am more impressed by the geniuses we have in house here at PT.