SOLUTION: May I have help w/ this one? 1) 3r +5s + t =0 3r –s –3t = 4 -3r-4s-4t= -19

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Question 1008286: May I have help w/ this one?
1)
3r +5s + t =0
3r –s –3t = 4
-3r-4s-4t= -19

Found 3 solutions by stanbon, mgmoeab, MathTherapy:
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
3r +5s + t =0
3r –s –3t = 4
-3r-4s-4t= -19
------
Subtract row 1 from row 2
Add row 1 to row 3
--------------
3r +5s + t =0
0 –6s –4t = 4
0 + s -3t = -19
-------
Interchange rows 2 and 3 to get::
3r +5s + t = 0
0 + s -3t = -19
0 –6s –4t = 4
====
Add 6 times row 2 to row 3 to get:
3r +5s + t = 0
0 + s -3t = -19
0 + 0 -22t = -110
--------------------------
Solve row 3 to get: t = 5
Solve row 2 to get: s = 3*5-19 = -4
Solve row 1 to get: r = (-5*-4 -5)/3 = 5
--------
Cheers,
Stan H.
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Answer by mgmoeab(37) About Me  (Show Source):
Answer by MathTherapy(10552) About Me  (Show Source):
You can put this solution on YOUR website!
May I have help w/ this one?
1)
3r +5s + t =0
3r –s –3t = 4
-3r-4s-4t= -19
  3r + 5s + t = 0 -------- eq (i)

  3r – s – 3t = 4 -------- eq (ii)

- 3r - 4s - 4t = - 19 ---- eq (iii)



   s - 3t = - 19 ----- Adding eqs (i) & (iii) ------- eq (iv)

- 5s - 7t = - 15 ----- Adding eqs (ii) & (iii) ------ eq (v)

  5s - 15t = - 95 ---- Multiplying eq (iv) by 5 ----- eq (vi)

     - 22t = - 110 --- Adding eqs (v) & (vi)

t+=+%28-+110%29%2F%28-+22%29, or highlight_green%285%29



s - 3(5) = - 19 ---------- Substituting 5 for t in eq (iv)

s - 15 = - 19

s = - 19 + 15, or highlight_green%28-+4%29



3r + 5(- 4) + 5 = 0 ------ Substituting - 4 for s, and 5 for t in eq (i)

3r - 20 + 5 = 0

3r - 15 = 0

3r = 15

r = 15%2F3, or highlight_green%285%29