find the sum of series 6^2+7^2+8^2+.........+21^2
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you have to do
36+49+64+81+100+121+144+162+196+225+256+289+324+361+400+441= 3256
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4
Answer:
3256
Step-by-step explanation:
Sn = n (n+1)(2n+1 )/6
6^2+7^2+8^2+.........+21^2 = sum of 21t erms - sum of 5 terms
= (21x22x43 - 5x6x11 )/6 = 77 x 43 - 55 = 11(301 -5 ) = 11x 296 = 3256
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