Algebra 2 help needed on systems of linear equations....

[1cat2ferrets]

in 3 variables!! My son and I are nearly in tears trying to figure this problem out. Very confusing, to say the least!!:confused:

Here it is:
3x^2+4y+z=7
2y+z=3
-5x+3y+8z=-31

Thanks to anyone that can help us figure it out!!

[NicksMama-Zack's Mama Too]

but here is a free website with some help...

http://www.mathway.com/problem.aspx?p=algebra


K

[Jann in TX]

does the first equation have an x squared?

Much easier to deal with if it doesn't!

Also--has he been using the 'elimination' method or is he using matrices yet?

[MyThreeSons]

Here it is:
3x^2+4y+z=7
2y+z=3
-5x+3y+8z=-31


Assuming you've mastered 2 equations with 2 unknowns, one way to tackle this problem would be to solve the middle equation for z:

z = 3 - 2y

Plug that expression in for z in the first and third equations, and you have 2 equations with 2 unknowns. Solve those for x and y, then go back to the middle one and solve for z.

Note: having that x^2 term in the first equation definitely complicates things.

HTH

[annabanana1992]

If these are supposed to be systems of linear equations why is there an x squared term?

[1cat2ferrets]

Yes, Jann, there's an x squared in the first equation. We finally found out how to do it after a couple of hours.
Thanks for your reply.

[1cat2ferrets]

Thanks for your help. We finally found out how to do this problem after awhile.

[1cat2ferrets]

That's what the problem stated and that's why we were confused, but figured it out after a couple of hours.
Thanks anyway!