Consider the sum sequence (an)n>0 = 4, 11, 18, 25, 32, … (a) What type of sequence is (an)nzo? Find an explicit formula an. (b) Is 249 in the sequence? Explain. (c) How many summands are in the sum 4 + 11 + 18+ 25 + (d) Compute the sum using Gauss' trick. • +249?

Advanced Engineering Mathematics
10th Edition
ISBN:9780470458365
Author:Erwin Kreyszig
Publisher:Erwin Kreyszig
Chapter2: Second-order Linear Odes
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Consider the sum sequence (an)n≥0 = 4, 11, 18, 25, 32, ....
(a) What type of sequence is (an)n≥o? Find an explicit formula an.
(b) Is 249 in the sequence? Explain.
(c) How many summands are in the sum 4 + 11 + 18 + 25 + . . . + 249?
(d) Compute the sum using Gauss' trick.
Transcribed Image Text:Consider the sum sequence (an)n≥0 = 4, 11, 18, 25, 32, .... (a) What type of sequence is (an)n≥o? Find an explicit formula an. (b) Is 249 in the sequence? Explain. (c) How many summands are in the sum 4 + 11 + 18 + 25 + . . . + 249? (d) Compute the sum using Gauss' trick.
Expert Solution
Step 1: Solution

(a) Given ann0=4, 11, 18, 25, 32, ....

a1=4a2=a1+7a3=a2+7=a1+2.7a4=a3+7=a1+3.7

Therefore we can notice that the  common difference 7 which we can compute by an-an-1

The first term is a1=4

Therefore the nth term is 

an=a+dn-1    =4+7n-1an=7n-3

Hence an=7n-3

 

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