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The value of `(.^(21)C_(1) - .^(10)C_(1)) + (.^(21)C_(2) - .^(10)C_(2)) + (.^(21)C_(3) - .^(10)C_(3)) + (.^(21)C_(4) - .^(10)C_(4)) + … + (.^(21)C_(10) - .^(10)C_(10))` is(A) `2^(21) - 2^(11)`(B) `2^(21) - 2^(10)`(C) `2^(20) - 2^(9)`(D) `2^(20) - 2^(10)`A. `2^(21) - 2^(11)`B. `2^(21) - 2^(10)`C. `2^(20) - 2^(9)`D. `2^(20) - 2^(10)` |
Answer» `(.^(21)C_(1) - .^(10)C_(1)) + (.^(21)C_(2) - .^(10)C_(2)) + (.^(21)C_(3) - .^(10)C_(3)) + …. + (.^(21)C_(10) - .^(10)C_(10))` `= (.^(21)C_(1) + .^(21)C_(2) + … + .^(21)C_(10)) - (.^(10)C_(1) + .^(10)C_(2) + ….+ .^(10)C_(10))` `= (1)/(2) (.^(21)C_(1) + .^(21)C_(2) + .... + .^(21)C_(20)) - (2^(10) - 1)` `= (1)/(2) (.^(21)C_(1) + .^(21)C_(2) + .... + .^(21)C_(21) - 1) - (2^(10) - 1)` `= (1)/(2) (2^(21) - 2) - (2^(10) - 1) = 2^(20) - 1 - 2^(10) + 1 = 2^(20) - 2^(10)` |
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