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