Question 1125262
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<U>HINT</U> :  The (r-1)-th term is equal to


<U>the sum of the first (r-1) terms</U>  MINUS  <U>the sum of the first (r-2) terms</U>, i.e.


5*(r-1)^2-2*(r-1)                  -       (5*(r-2)^2-2*(r-2)).
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Based on this hint, you can complete the assignment on your own by simplifying this expression.