Jawaban:

1) usia tono = T

usia iwan = I

usia joko = J

I + T + J = 41 ............... (1)

T = J - 2 ............ (2)

I = J + 1 ......... ..(3)

substitusi persamaan 2 dan 3 ke persamaan 1

I + T + J = 41

(J + 1) + (J - 2) + J = 41

J + 1 + J - 2 + J = 41

3J = 41 - 1 + 2

3J = 42

J = 42/3 = 14

T = J - 2 = 14 - 2 = 12

tahun lahir Toni = 2022 - 12 = 2010

2) x + 3y + 2z = 2 ,,,,,,,,,, (1)

2x - y + z = 5 ............(2)

3x - 2y - z = 3 .............(3)

eliminasi persamaan 1 dan 2

x + 3y + 2z = 2 [ ×2]

2x -y + z = 5 [ ×1 ]

2x + 6y + 4z = 4

2x - y + z = 5

---------------------- -

7y + 3z = -1 .......... (4)

eliminasi persamaan 2 dan 3

2x - y + z = 5 [ ×3 ]

3x -2y -z = 3 [ ×2 ]

6x - 3y + 3z = 15

6x - 4y - 2z = 6

---------------------- -

y + 5z = 9 .......... (5)

eliminasi persamaan 4 dan 5

7y + 3z = -1 [ ×1 ]

y + 5 z = 9 [ ×7 ]

7y + 3z = -1

7y + 35 z = 63

-------------------- -

-32z = -64

z = -64/ -32 = 2

masukkan persamaan 5

y + 5(2) = 9

y = 9 - 10 = -1

masukkan persamaan 1

x + 3 (-1) + 2 (2) = 2

x = 2 + 3 - 4 = 1

NILAI DARI 3X - Y + 6Z

= 3 (1) - (-1) + 6 (2) = 3 + 1 + 12 = 16