Jika (b+c, b-c) memenuhi sistem persamaan 3x - y + 2z = -1 dan -2x + y + 3z = -3, maka nilai b + c adalah ... A. 0 B. 1 C. 2 D. 3 E. 4

3x-y+2z=0 (subs (b+c , b-c)
3(b+c)-(b-c)+2z=0
3b+3c-b+c+2z=0
2b+4c+2z=0

-2x+y+3z=0 (subs (b+c, b-c))
-2(b+c)+(b-c)+3z=0
-2b-2c+b-c+3z=0
-b-3c+3z=0

2b+4c+2z=0 (×1) > 2b+4c+2z=0
-b-3c+3z=0 (×2) > -2b-6c+6z=0
-------------------(+)
-2c+8z=0 > c= 4z
-b-3c+3z=0 > -b-3(4z)+3z=0 > -b-12z+3z=0 > -b-9z=0
b= -9z

b:c
-9z:4z
-9:4
b+c= -9+4=-5