On a cartesian coordinate plane, point a is at (-2, 2) and point b is at (1, -4) what is the equation for line ab

The slope of this line is

         2-(-4)
m = = -6/3 = -2.
        -2 - 1

Starting with y = mx + b, -4 = -2(1) + b, or     -4 = -2 + b.  Then b= -2, and the
equation is

y = -2x -2.

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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.