Mathematics
Senior High
（４）がわかんなくて1番上の=の後はどうなってますか？😭😭
k=1
21
21
(4) Σk² = Σk² - Σk²
k=7
k=1
k = 1
===
=1/12
6
9
n
・21(21+1)(2.21 +1)
1
･・ 6(6+ 1)2.6 + 1 )
6
=3311-913220
n
n
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