in an Ap.ifa=-2and a3=4,then an=--------
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Answer:
a
n
=3−4n
a
1
=3−4(1)=−1
a
2
=3−4(2)=−5
a
3
=3−4(3)=−9
a
3
−a
2
=a
2
−a
1
=−4
as it should shows constant common difference
∴ It is an AP with a=−1 & d=−4
S
20
=
2
20
[2(−1)+(20−1)(−4)]
S
20
=10[−2−76]
S
20
=−780.
Step-by-step explanation:
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