Expert: Sherman D. - 12/9/2008

Question
#1

36x -15y +50z = -10
2x +25y = 40
54x - 5y +30z = -160



#2

1.8x -z = 0.7
1.2y +z = -0.7
1.5x -3y = 3  

Answer
1.)
36x - 15y + 50z = -10
2x + 25y = 40
54x - 5y + 30z = -160

2x + 25y = 40
2x = -25y + 40
x = (-25/2)y + 20

36((-25/2)y + 20) - 15y + 50z = -10
54((-25/2)y + 20) - 5y + 30z = -160

-450y + 720  - 15y + 50z = -10
-675y + 1080 - 5y + 30z = -160

-465y + 50z = -730
-680y + 30z = -1240

multiply top by -3 and bottom by 5

1395y - 150z = 2190
-3400y + 150z = -6200

2005y = =-4010

y = 2

x = (-25/2)(2) + 20
x = -25 + 20
x = -5

36(-5) - 15(2) + 50z = -10
-180 - 30 + 50z = -10
50z = 200
z = 4

ANS:
x = -5
y = 2
z = 4

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2.)
1.8x - z = 0.7
1.2y + z = -0.7
1.5x - 3y = 3

18x - 10z = 7
12y + 10z = -7

18x + 12y = 0
15x - 30y = 30

3x + 2y = 0
x - 2y = 2

4x = 2
x = (1/2)

(18/10)(1/2) - z = (7/10)
(18/20) - z = (7/10)
-z = (-9/10) + (7/10)
z = (9/10) - (7/10)
z = (2/10)

(12/10)y + (2/10) = (-7/10)
12y + 2 = -7
12y = -9
y = (-9/12)
y = (-3/4)

ANS :
x = (1/2)
y = (-3/4)
z = (1/5)