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Limits and Derivatives · Question 19

JEE Main 2025 (Online) 28th January Evening ShiftNumericalMedium📈 Topic in 10% papers+4
1

Let f(x) = n r=0n ( (x/2r+1 ) + 3 (x/2r+1 )1 - 2 (x/2r+1 ) ). Then x 0 ex - ef(x)(x - f(x)) is equal to .

Answer

1

Solution

Let t = . Then

2 - = 2t1 - t2 - t = t + t31 - t2

With = x2r+1, the r-th term = x2r - x2r+1

r=0n = x - x2n+1 (telescoping)

As n , x2n+1 0 f(x) = x

Limit = x 0 e x ex - x - 1x - x

As x 0, x - x 0 and e x 1

Limit = 1 1 = 1

Answer: 1

JEE Main 2025 (Online) 28th January Evening Shift

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