What are the first 4 terms of the arithmetic sequence in the graph?

In an arithmetic sequence, whose first term is a and difference between a term and its preceding term is d,

       the nth term is a+(nâ’1)d and sum of first n terms is n2(2a+(nâ’1)d)

Hence 6th term will be a+5d=8 and 10th term will be a+9d=13

       Subtracting first from second, 4d=5 or d=1.25 and a=8â’5â‹…1.25=8â’6.25=1.75

       Hence sum of first four terms is 42â‹…(2â‹…1.75+3â‹…1.25)=2â‹…(3.5+3.75)=2â‹…7.25=14.50

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