Question

if the 18th term of an AP is 37 and the 15th term is 15 more than its 12th term. Find AP and the sum of first 15 terms​

Answer 1

Step-by-step explanation:

a(18)=a+(18-1)d=37

=>a+17d=37............(i)

a(15)=a+(15-1)d=a+14d

a(12)=a+(12-1)d=a+11d

Now according to the question....

the 15th term is 15 more than its 12th term.

So...

a(12)+12=a(15)

a+11d+12=a+14d

12=14d-11d

3d=12

d=4

Now,, a=37-17(4)

=37-68

= - 31

S(15)=(15/2)[2(-31)+(15-1)4]

=(15/2)(-62+56)

=(15/2)(-6)

=-45

THe sum of first 15 terms is=-45

And the Ap series is...

-31,-27,-23,-19,-15,-11,-7,-3,1,5,9,13,...........

Hope this helps you

Answer 2

Answer:

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