Who is asking: Student
The number zero plays a very special role in our number system. Suppose, for example, that I tell you that I multiplied two numbers and got the answer 12. This does not tell you very much about the two numbers. They might be 3 and 4, or 2 and 6, or 1 and 12, or 24 and 1/2, ... However if I tell you that I multiplied two numbers and got the answer 0 then you know that one of the numbers must be 0. In fact they might both be zero, but I know for sure that at least one of them is 0.
Thus, if you multiply the two numbers g and g + 5 and get the answer 0, then either g = 0 or g + 5 = 0. If g + 5 = 0 then g = -5 and hence if