Question

Diketahui sistem persamaan 4x + 7y = 5 dan x + y= -1. Tentukan nilai 4x + 3y !

Answer 1

4x+7y=5.. (pers1)
x+y=-1... (pers2)
*eliminasi pers1 dan 2 (dikurangi)
(pers1) x1 4x+7y=5
(pers2) x4 4x+4y=-4
⇔3y=9
⇔y=3
masukin ke pers 2
x+y=-1
⇔x+(3)=-1
⇔x=-1-3=-4

4x+3y= 4(-4)+3(3)= -16+9= -7

Answer 2

X + y = -1
x = -1 - y

4x + 7y = 5
4(-1-y) + 7y = 5
-4 - 4y + 7y = 5
3y = 5 + 4
3y= 9
y= 3

x = -1 -y = -1 - 3 = -4
jadi :
4x + 3y = 4x-4 + 3x3 = -16 + 9 = -7