The first five terms of the quadratic sequence are



   a     1    -6     b    -4



The second differences of a quadratic sequence are constant.



   a      1    -6       b      -4   the sequence

     1-a    -7    b+6      -b-4     first differences

         a-8  b+13   -2b-10         second differences



So a-8 = b+13 = -2b-10.  Then











And then











ANSWERS:



The first term is a = 40/3

The constant second difference is a-8 = 16/3 

Answer by Edwin McCravy(20062)   (Show Source): You can put this solution on YOUR website!
 

An alternate method is to find the general term by substituting in 

     an²+bn+c = the nth term



and solving for a,b,c.

Edwin



 

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