Question

Find the sum of first 25 terms of an AP whose nth tern is 1-4n

Answer 1

Answer:

its -1275

Step-by-step explanation:

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Answer 2

Answer:

Here it is given that, an = 1 - 4n

putting, n =1 , a1 = 1- 4(1) = -3

putting, n =2 , a2 = 1 - 4(2) = -7

Therefore, a = -3 and d = (-4)

so, S25 = 25/2 [ 2(-3) + 24 (-4)]

= 25/2 [-102]

= 25 (-51 )

= -1275 Ans

hence, the sum of first 25 terms of an AP whose nth term is 1 -4n is -1275