Question

已知a、b为整数,a-2b=4,ab＋c的二次方-1＝0,求a+b+c

Answer 1

a-2b=4
a=2b+4
ab+c^2-1=0
(2b+4)b=1-c^2
2(b+1)^2=3-c^2
2(b+1)^2>=0
3-c^2>=0
c=0,-1,1
c=0,a,b不是整数,舍去
c=1,-1,ab=0 a=0,或b=0
a=0,b=-2,a+b+c=-3,-1
b=0,a=4,a+b+c=3,5
综上:-3,-1,3,5