Consider the sequence of functions `(x) = 1/{1+x^n}` for `x \in [0,1]`. Check whether the sequence of functions `f_n (x)` converges uniformly on [0,1].
Consider the sequence of functions `(x) = 1/{1+x^n}` for `x \in [0,1]`. Check whether the sequence of functions `f_n (x)` converges uniformly on [0,1].
Solution:
To check whether the sequence of functions `f_n(x) = 1/(1+x^n)` converges uniformly on the interval [0,1], we need to analyze the behavior of the sequence as n approaches infinity.
For a sequence of functions to converge uniformly, the limit function must satisfy the following condition: For any ε > 0, there exists an integer N such that for all x in the interval [0,1] and for all n ≥ N, the difference between `f_n(x)` and the limit function, denoted as f(x), must be less than ε.
Let's examine the behavior of the sequence. For any fixed x in the interval [0,1], as n increases, the term `x^n` becomes smaller. Consequently, the denominator `1 + x^n` becomes larger, leading to the fraction `1/(1+x^n)` approaching zero.
If we take the limit as n approaches infinity, we can evaluate the limit function f(x) by substituting n = ∞ into the expression:
`f(x) = 1/(1+x^∞) = 1/(1+0) = 1/1 = 1`
Therefore, the limit function is f(x) = 1 for all x in the interval [0,1].
Now, let's examine the uniform convergence. For a given ε > 0, we need to find an integer N such that for all n ≥ N and for all x in the interval [0,1], `|f_n(x) - f(x)| < ε`.
Let's choose an arbitrary x in the interval [0,1] and evaluate `|f_n(x) - f(x)|`:
`|f_n(x) - f(x)| = |1/(1+x^n) - 1|`
To simplify further, we can find the maximum value of `|f_n(x) - f(x)|` within the interval [0,1].
If we differentiate `|f_n(x) - f(x)|`with respect to x and equate it to zero, we find the critical points of the expression `1/(1+x^n)`. However, since x^n is strictly increasing for x ∈ [0,1], the maximum value occurs at either x = 0 or x = 1.
Evaluating `|f_n(0) - f(0)| and |f_n(1) - f(1)|`:
`|f_n(0) - f(0)| = |1/(1+0^n) - 1| = |1/(1+0) - 1| = |1 - 1| = 0`
`|f_n(1) - f(1)| = |1/(1+1^n) - 1| = |1/(1+1) - 1| = |1/2 - 1| = 1/2`
We can observe that `|f_n(0) - f(0)| = 0` for all n, indicating that the sequence of functions converges pointwise at x = 0. However, `|f_n(1) - f(1)| = 1/2`, which does not approach zero as n tends to infinity. Therefore, the sequence of functions `{f_n(x)}` does not converge uniformly on the interval [0,1].
In conclusion, the sequence of functions `f_n(x) = 1/(1+x^n)` does not exhibit uniform convergence on the interval [0,1].
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