If the square of a-3ab-4b = 0, then the value of a / B is?

If the square of a-3ab-4b = 0, then the value of a / B is?

a²-3ab-4b²=0
(a-4b)(a+b)=0
a-4b=0,a+b=0
a=4b,a=-b
So a / b = 4 or - 1