Diketahui x₁ dan y₁ memenuhi sistem persamaan:
2x + 3y = 11
5x – 2y = -39
Nilai 7x₁ + y₁ = ...
Pembahasan:
2x + 3y = 11 |×2|4x + 6y = 22
5x – 2y = -39|×3|15x – 6y = –177 ₊
19x = –95
x = –5
2x + 3y = 11
2(-5) + 3y = 11
-10 + 3y = 11
3y = 21
y = 7
7x₁ + y₁ = 7(-5) + 7
= -35 + 7
= -28