B1.c)1-2-3+4+5-6-7+8+...+801-802-803+804
=(1-2-3+4)+...+(801-802-803+804)
=0+0+...+0
=0
B3:
a)xy=-31
TCBS: x -31 -1 1 31
y 1 31 -31 -1
b)(x-2)(y+1)=32
Vì x,y∈Z nên =>x-2 và y+1∈Z
=>TCBS: x-2 -32 -16 -8 -4 -2 -1 1 2 4 8 16 32
y+1 -1 -2 -4 -8 -16 -32 32 16 8 4 2 1
x -30 -14 -6 -2 0 1 3 5 6 10 18 34
y -2 -3 -5 -9 -17 -33 31 15 7 3 1 0