Desperate need of Algebra 2 help

[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!

---------------------

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.

[Barbara]

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

Like 20 minutes? After finding that in the first try I had only multiplied the left hand of the equation and in the second try I had multiplied 5*25= 50

[smokey the elder]

Wow! That's great. I remembered that you needed to get down to two equations in terms of x and y, but got stuck after that!

[Daisy and Delilah]

I am alot more rusty than I thought. Awesome!!!

[slick]

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

Ahhhh, yeah....what she said!!! Barbara, you never cease to amaze me. I really don't have a clue what you are talking about, but it sure sounds good!