diketahui sistem persamaan 4 x + 5 y = 14 dan 5× - 2y = 2 maka nilai dari 10 x + y =...

Mapel : Matematika
Kelas : VIII SMP
Bab : SPLDV

Pembahasan :
4x + 5y = 14 |x 2| 8x + 10y = 28
5x - 2y = 2 |x 5| 25x - 10y = 10

Eliminasi keduanya...
25x - 10y = 10
8x + 10y = 28
————————— (+)
33x = 38
x = 38/33

Substitusi x ke Persamaan II
5x - 2y = 2
5(38/33) - 2y = 2
2y = 190/33 - 66/33
2y = 124/33
y = 124/66
y = 62/33

Maka nilai :
10x + y
= 10(38/33) + (62/33)
= 380/33 + 62/33
= 442/33
= 13 (13/33)

4x + 5y = 14 (×5)
5x - 2y = 2 (×4)

20x + 25y = 70
20x - 8y = 8
------------------------ -
33y = 62
y = 62/33

4x + 5y = 14
4x + 5(62/33) = 14
4x + 310/33 = 14
4x = 14 - 310/33
4x = 462/33 - 310/33
4x = 152/33
x = 152/132
x = 38/33

10x + y = 10×(38/33) + 62/33
= 380/33 + 62/33
= 442/33
= 13 13/33