g²-32g+256
This means we need to find something to add to -32 and multiply to 256. However, we can first reconize that 256 is 16². And since 256 is positive, that means that both 16's have to be negative to add to -32.
Therefore:
g²-32g+256
(g-16)(g-16)
(g-16)²
Therefore, (g-16) is one of the factors