tentukan penyelesaian dari persamaan: 3x + 4y - 5z = 12, 2x + 5y + z = 17 , 6x - 2y + 3z = 17 ... dengan metode 1. eliminasi 2.substitusi.... makasih

1)
3x + 4y - 5z = 12 (× 1)
2x + 5y + z = 17 (× 5)

..3x + .. 4y - 5z = 12
10x + 25y + 5z = 85
----------------------------- +
13x + 29y = 97 (I)

3x + 4y - 5z = 12 (× 3)
6x - 2y + 3z = 17 (× 5)

..9x + 12y - 15z = 36
30x - 10y + 15z = 85
------------------------------ +
39x + 2y = 121 (II)

(I)....13x + 29y = 97 (× 3)
(II)...39x + 2y = 121 (× 1)

39x + 87y = 291
39x + ...2y = 121
------------------------- -
85y = 170
y = 170/85
y = 2

39x + 2y = 121
39x + 2(2) = 121
39x + 4 = 121
39x = 121 - 4
39x = 117
x = 117/39
x = 3

2x + 5y + z = 17
2(3) + 5(2) + z = 17
6 + 10 + z = 17
16 + z = 17
z = 17 - 16
z = 1

Jadi HPnya adalah {3 , 2 , 1}

2)
3x + 4y - 5z = 12
3x + 4y - 12 = 5z
z = (3x + 4y - 12)/5

2x + 5y + z = 17
2x + 5y +(3x + 4y - 12)/5 = 17
(10x)/5 + (25y)/5 +(3x + 4y - 12)/5 = 17
(10x + 25y + 3x + 4y - 12)/5 = 17
13x + 29y - 12 = 17 × 5
13x + 29y - 12 = 85
13x + 29y = 85 + 12
13x + 29y = 97 (I)

6x - 2y + 3z = 17
6x - 2y + 3(3x + 4y - 12)/5 = 17
6x - 2y + (9x + 12y - 36)/5 = 17
(30x)/5 - (10y)/5 + (9x + 12y - 36)/5 = 17
(30x - 10y + 9x + 12y - 36)/5 = 17
39x + 2y - 36 = 17 × 5
39x + 2y - 36 = 85
39x + 2y = 85 + 36
39x + 2y = 121 (II)

(I)...13x + 29y = 97
(II)..39x + 2y = 121

13x + 29y = 97
13x = 97 - 29y
x = (97 - 29y)/13

39x + 2y = 121
39(97 - 29y)/13 + 2y = 121
3(97 - 29y) + 2y = 121
291 - 87y + 2y = 121
291 - 85y = 121
-85y = 121 - 291
-85y = -170
y = -170/-85
y = 2

x = (97 - 29y)/13
x = (97 - 29(2))/13
x = (97 - 58)/13
x = 39/13
x = 3

2x + 5y + z = 17
2(3) + 5(2) + z = 17
6 + 10 + z = 17
16 + z = 17
z = 17 - 16
z = 1

Jadi HPnya adalah {3 , 2 , 1}