Question

o If the Sum of first four terms of an AP is
40
and that of first 14 terms is 280.
find the sum of its first n terms.​

Answer 1

Answer:

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Step-by-step explanation:

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Answer 2

Answer:

s4=40

4/2 (a+(4-1)d)=40

2 (a+3d)=40.......... (1)

a+3d=20

s14=280

14/2 (a+(14-1)d)=280

7 (a+13d)=280

a+13d=40

a+13d=2 (a+3d)...... (from 1)

proceed with this process and you will get your answer

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