4 + 44 + 444 + ............ ধারাটির n-সংখ্যক পদের যোগফল নির্ণয় কর।
Solution
Correct Answer: Option D
a + aa + aaa + …………… n সংখ্যক পদের যোগফল
S = (a/9){(10/9)(10n-1) - n}
= (4/9){(10/9)(10n - 1) - n
= (40/81)(10n-1) - (4/9)n
S = (a/9){(10/9)(10n-1) - n}
= (4/9){(10/9)(10n - 1) - n
= (40/81)(10n-1) - (4/9)n
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