Question

Q. 13. 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
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Answer 1

Answer:

hello how r u

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by the way the answer to ur question is here

Step-by-step explanation:

let difference =d

first term =a

and number of terms in first case b 4 n in second case b 14

=> 4=a+(4-1)d

4=a+3d (i)

=> 14=a+(14-1)d

14=a+13d (ii)

solving (i) n (ii)

a+3d = 4

-a+13d=14

=0-10d=-10

=> cut minus from both sides

=> 10d=10

divide whole equation by 10

=>d=10

Answer 2

Answer:

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