If the n th term of a sequence is 3-2n. Find the sum of fifteen terms.
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If the n th term of a sequence is 3-2n. Find the sum of fifteen terms.
If the n th term of a sequence is 3-2n. Find the sum of fifteen terms.
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Step-by-step explanation:
First term, a=1,15
th
term a
15
=3−30=−27
Sum of 15 terms =
2
n
(a+l(lastterm))=
2
15
(1−27)=15(−13)=−195
Answer:
193
Step-by-step explanation:
3-2n put the value 1,2,3,....
than 1,-1,-3 this series in AP.
so,
a+(n-1)d = 3-2n ----(1)
put n = 1 in eq 1
so a + 0.d = 3 - 2*1
a = 1
again put n= 2 in eq 1
1 + d = 3-4
d = -2 or 2
than sun of 15 term = n/2*(2a+(n-1)*d)
put all the value so = 193