We know the product of two factors, say a and b is zero, that means that:
a * b = 0
We also know one of the factors is also zero, say a = 0:
0 * b = 0
Now one of the properties of the product is that if at least one of the factors is zero, the result is zero regardless of the values of the other factors.
For example, if b = 4
0*4 = 0
If b=-4
0 * (-4) = 0
So we can choose any value for b and the product will always be zero.
This means we cannot determine the value of b because it could be anything.
