Question

Write the sum using summation notation, assuming the suggested pattern continues.

-4 + 5 + 14 + 23 + ... + 131

Answer 1

it is an A.P
find the number of terms by the formula tn=a+(n-1) d
tn=131
a=-4
d=5-(-4)=5+4=9
then sum \[Sn=\frac{ n }{ 2 }\left( a+tn \right)\]

Answer 2

@surjithayer these are my answer choices

Answer 3

find n first by the formula i gave in the beginning.

Answer 4

131=-4+(n-1)9
131+4=9n-9
135+9=9n
n=16

Answer 5

\[\sum_{0}^{15}(-4+9n)\]
0,1,2,...,15 are 16 terms.
when n=0,a=-4
when n=15,tn=-4+9*15=-4+135=131