If Sn=n² find S1, S2 , a1,a2 show that an= 2n+1
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Answer:
s
n
=2n
2
+3n
T
n
=s
n
−s
n−1
=2n
2
+3n−2(n−1)
2
−3(n−1)
=2n
2
+3n−2n
2
+2n−2−3n+3
=3n−2+n+3
=4n+1
T
1
=4+1=5
T
2
=8+1=9
d=−T
1
+T
2
d=9−5=4
Step-by-step explanation:
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