Question

Persamaan 3 variabel.
2a - 5b+c= -5
3a + b + 4c = 23
a-2b+3c=4
Tentukan nilai a-b+c

Answer 1

A=4
b=3
c=2
a-b+c=4-3+2=1+2=3

Answer 2

2a - 5b + c = -5 |x 1| 2a - 5b + c = -5
3a + b +4c = 23 |x 5| 15a + 5b + 20 c = 115
______________________________ +
17a + 21c = 110

2a - 5b + c = -5 |x 2| 4a - 10b + 2c = -10
a - 2b +3c = 4 |x 5| 5a - 10b + 15c = 20
______________________________-
-a + 17c = - 30

17a + 21c = 110 |x 1| 17a + 21c = 110
-a + 17c = - 30 |x 17| -17a + 289c = -510
______________________________+
310c = -400
c = -40/31

-a + 17c = - 30
-a + 17.-40/31 = -30
-a - 680/31 = -30
-a = -30 +680/31
-a = -930/31 + 680/31
-a = -250/31
a = 250/31


2a - 5b + c = -5
2. 250/31 - 5b -40/31 = -5
500/31 - 5b -40/31 = -5
460/31 -5b = -5
-5b = -5 - 460/31
-5b = -155/31 - 460/31
-5b = -615/31
b = 615/(31.5)
b = 615/155
b = 123/31

a - b + c
=250/31 - 123/31 + (-40/31)
=87/31
=2 25/31
=2,8065