Math, asked by yuvisingh77770, 7 months ago

find the sum of first 17 term of an AP whose 4 and 9 term is -15 and -30 respectively​

Answers

Answered by rajeevr06
0

Answer:

a+3d = –15....(i)

a+8d = –30....(ii)

apply (ii) – (i), we get

5d = –15

d = –3

putting value of d in (i),

a+3(–3) = –15

so, a = –15+9 = –6

 s_{17} =  \frac{17}{2} (2 \times ( - 6) + 16 \times ( - 3))

 =  \frac{17}{2} ( - 12 - 48) =  - 60 \times  \frac{17}{2}  =

 - 30 \times 17 =  - 510

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