Question

Name the constant differences of the sequence 20, 21, 26, 35, 48...

What does "constant differences" mean?

Thank you so much! :)

Answer 1

suppose you subtract the second - first = 1
third - second = 5
fourth - third = 9
fifth - fourth = 13

to get the "first differences" of 1,5,9,13

now suppose we repeat the same procedure

5-1 = 4
9-5 = 4
13-9 = 4

notice we now have "constant differences" but we had to do it twice.

general concept:
if the first differences are constant, then the data came from a first degree relation
if the second differences are constant, then the data came from a second degree, or quadratic relation
if the third ....

Answer 2

This site may help.

http://www.icoachmath.com/SiteMap/ConstantFunction.html