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The largest value of `x`for which the fourth tem in the expansion `(5^2/3(log)_5sqrt(4^(x+44))+1/(5^(log)_5 2^((x-1)+7 3)))`is 336 is. |
Answer» Correct Answer - 4 `(5^(2/5sqrt(4^(2)+44))+(1)/(5^(log2sqrt(2^(2-1))+7)))^(8)` `= ((sqrt(4^(4)+44)^(2//5))+((1)/(3sqrt(2^(x-1)+7))))^(8)` `= ((4^(x)+44)^(1//5)+(1)/((2^(x-1)+7)^(1//3)))^(8)` Now, `T_(4) = T_(3+1)=.^(8)C_(3)((4^(x)+44)^(1//5))^(8-3)(1)/((2^(x-1)+7)^(1//3))^(3)` Given `336 = .^(8)C_(3)((4^(x) + 44)/(2^(x-1) + 7))` Let `2^(x) = y` `rArr 336 = .^(8)C_(3)((y^(2)+44)/((y//2)+7))` or `336 = (8xx7xx6)/(3xx2xx1)((2(y^(2)+44))/(y+14))` `rArr y^(2) -3y + 2 =0` or `y = 0,2` or `y = 2` or `x= 4` |
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