How do you find the first five terms given #a_1=2# and #a_(n+1)=a_n-n#?

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Answer 1 · 2016-11-03T05:03:39

First five terms are #{2,1,-1,-4,-8}#

#a_1=2#

Now as #a_(n+1)=a_n-n#

#a_2=a_(1+1)=a_1-1=2-1=1#

#a_3=a_(2+1)=a_2-2=1-2=-1#

#a_4=a_(3+1)=a_3-3=-1-3=-4#

#a_5=a_(4+1)=a_4-4=-4-4=-8#

Hence first five terms are #{2,1,-1,-4,-8}#