व्हाट इज द सम ऑफ द फर्स्ट टर्म्स ऑफ एन ए पी एफ
Answers
Answer:
Step-by-step explanation:
We have,
S
n
=4n−n
2
Taking n=1 and we get,
S
1
=4×1−1
2
=4−1
S
1
=3
So, the sum of fristr term of an A.P. is 3.
But, sum of first term will be the first term.
So, first term a=3.
Now, taking n=2 and we get,
S
n
=4n−n
2
S
2
=4×2−2
2
S
2
=4
Then, sum of first 2 terms is 4.
Now, finding Secondterm.
Then,
According to given question,
Firstterm+Secondterm=4
3+a
2
=4
a
2
=1
Hence the A.P.is
First term a=3
Common difference
d=Secondterm-firstterm
d=1-3
=-2
The third term of
a
3
=a+2d
a
3
=3+2×(−2)
a
3
=−1
Similarly, 10
th
term
a
10
=a+9d
=3+9(−2)
=3−18
=−15
Then,
n
th
termis
a
n
=a+(n−1)d
a
n
=3+(n−1)(−2)
a
n
=3−2n+2
a
n
=5−2n
Hence, this is the answer.