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