Mathematics
Senior High
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この書き方だとだめですか?
n-1
n-1
(4) Σk(k+4)=(k²+4k)
k=1
k=1
n-1
n-1
=Σk² +4Σk
=
=
=
k=1
6
6
k=1
(n-1)n (2n-1)+4(n−1)n
(n-1)n(2n-1)+2(n−1)n
(n−1)n{(2n−1)+12}
6
=
1
———
(n-1)n(2n+11)
= fn (n-1) (2h +11)
ass
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わかりました!ありがとうございます!