Question

If the nth terms of a sequence is 3 - 2n,
find the sum of fifteen terms.
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Answer 1

Answer:

answer is -195

Step-by-step explanation:

$a_{n}$=3+2n

if n=1 then,

a=3-2(1)

=1

if n=2 then,

$a_{2}$=3-2(2)

  =-1

$a_{3}$=3-2(3)

  =-3

so ap is 1,-1,-3,.................................

so a=1, d=-2, n=15,$s_{n}$=?

$S_{n}$=15/2{2(1)+(15-1)(-2)}

   =15/2{2+(-28)}

   =15/2{-26}

   =-195

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