38. Jika 2x + 5y = -7 dan 3x - 2y = 18, maka nilai

4x + 5y adalah ….
a. -1
c. 2
b. 1
d. 5

38. Jika 2x + 5y = -7 dan 3x – 2y = 18, maka nilai

Jawaban:

B.1

Penjelasan dengan langkah-langkah:

$left { {{2x + 5y = - 7} atop {3x - 2y =18 }} right. \ \ left { {{ 2(2x + 5y) = 2 times ( - 7)} atop {5(3x - 2y) = 5 times 18}} right. \ \ left { {{2 times 2x + 2 times 5y = - 14} atop {5 times 3x - 5 times 2y = 90}} right. \ \ left { {{4x + 10y = - 14} atop { 15x - 10y = 90}} right. \ \ 4x + 10y + 15x - 10y = - 14 + 90 \ 19x = 76 \ x = 76 div 19 \ x = 4 \ \ 2 times 4 + 5y = - 7 \ 8 + 5y = - 7 \ 5y = - 7 - 8 \ 5y = - 15 \ y = - 15 div 5 \ y = - 3 \ \ (x.y) = (4. - 3) \ \ 4x + 5y \ 4 times 4 + 5 times ( - 3) \ 16 - 15 \ = 1$