Chapter 11 - Section 11.4 - Partial Sums of Arithmetic and Geometric Sequences - Exercise Set - Page 659: 33

$a_2=3950$ $a_3=3900$ $a_4=3850$

First, we find that the common difference is 50. This allows us to find the next terms in the sequence, given the starting number. Note, to get a given term, subtract the common difference from the previous term. $a_2=4000-50=3950$ $a_3=3950-50=3900$ $a_4=3900-50=3850$