liliy 3 years ago matrix: 2x+3y+ 7z= 13 3x+2y - 5z = -22 5x+7y - 3z = -28

1. liliy

@phi can you help me?

2. precal

use elimination

3. liliy

what does that mean?

4. precal

multiply -3 to the first equation multiply 2 to the second equation

5. liliy

we have to use matrix

6. precal

idea is to get rid of one variable at a time matrix - even better can you put it in the calculator?

7. precal

|dw:1338861644110:dw|

8. liliy

hahah. no calculators.. this is linear algebra

9. precal

yes, well the idea is still the same except with not using the variables

10. precal

sorry it has been a long time since I have done linear algebra. I just remember it was my favorite course during my undergrad days....... :)

11. liliy

i dont understand the matrix . can you brief me, i feel like my numbers are always wrong and then the whole thing is wrong

12. liliy

if i get a matrix of numbers and when it simplifies: 1 0 3 8 0 0 9 3 0 0 8 9

13. liliy

these are arbitrarty numbers but if i get two rows that have 0 0 does that mean its bad?

14. precal

|dw:1338861963247:dw| this is your goal in the end

15. precal

if it has a solution

16. liliy

right, but if you have any rows that are all zeros that means what?

17. precal

|dw:1338862078583:dw|

18. liliy

k, like:: 2 4 6 -8 3 6 7 10

19. precal

this one has a solution x=-1, y=-2, z=3

20. precal

|dw:1338862146454:dw| you goal is to create that solution form (sorry I can't even remember its official name, may I be forgiven by the math gods) I would multipy the first row by (1/2) that would force that first term to turn into a 1 but don't forget to change all the other numbers in that row

21. precal

I think that is called row multiplication

22. precal
23. liliy

got it, but for the little example i just posted: 2 4 6 -8 3 6 7 10, this matrix, i get the bottom row is 0 0 .. and none of the multiple choices look like that, what am i doing wrong?

24. precal

not sure, I put it in my calculator and it does have a solution

25. precal

sorry reposted your question but label it, must use the matrix (linear algebra) good luck :) sorry