Question

find the sum of first 25terms of ap whose n* is givan: 3n sum 2

Answer 1

sum of 1st 25 terms ap will be
s=n/2(2a+(n-1)d)
were 'a'1st term ,n is no terms,d is commn diffrence
rest of quez doesn't make sense

hope u understood!!

Answer 2

Answer:

Step-by-step explanation:

|n=7-3n

|1=7-3×1=7-3=4

|2=7-3×2=7-6=1

|3=7-3×3=7-9=-2

First term=a=4

Common diff.=d=|2-l1=1-4=-3

Sum of 25 terms=sn= n/2[2a+(n-1)d] =25/2[2×4+(25-1)-3]

=25/2[8-72]

=25/2×-64

=-800

HENCE SUM IS -800

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