The product of a number (n-1) and the number (n+1) is always equal to ?

It is an identity n^2-1. That is n square minus 1

The major difference is that a histogram is only used to plot the frequency of score occurrences in a continuous data set that has been divided into classes, called bins.  bar charts, on the other hand, can be used for a great deal of other types ofvariables  including  ordinal  andnominal  data sets.