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Let 
f(x)=(x+1)/(xe^(x)+e^(x)) when 
x!=-1.

f is continuous for all real numbers.
Find 
f(-1).
Choose 1 answer:
(A) 
e
(B) 2
(C) 1
(D) 
-2e

Let f(x)=x+1xex+ex f(x)=\frac{x+1}{x e^{x}+e^{x}} when x1 x \neq-1 .\newlinef f is continuous for all real numbers.\newlineFind f(1) f(-1) .\newlineChoose 11 answer:\newline(A) e e \newline(B) 22\newline(C) 11\newline(D) 2e -2 e

Full solution

Q. Let f(x)=x+1xex+ex f(x)=\frac{x+1}{x e^{x}+e^{x}} when x1 x \neq-1 .\newlinef f is continuous for all real numbers.\newlineFind f(1) f(-1) .\newlineChoose 11 answer:\newline(A) e e \newline(B) 22\newline(C) 11\newline(D) 2e -2 e
  1. Finding f(1)f(-1): We need to find the value of f(1)f(-1). However, we cannot directly substitute x=1x = -1 into the function because the function is not defined at x=1x = -1. We will use the limit process to find the value of f(x)f(x) as xx approaches 1-1.
  2. Using the limit process: Let's consider the limit of f(x)f(x) as xx approaches 1-1:limx1f(x)=limx1x+1xex+ex\lim_{x \to -1} f(x) = \lim_{x \to -1} \frac{x+1}{xe^{x}+e^{x}}
  3. Applying L'Hôpital's Rule: We can see that if we substitute x=1x = -1 directly, we get 0/00/0, which is an indeterminate form. To resolve this, we can apply L'Hôpital's Rule, which states that if the limit of f(x)/g(x)f(x)/g(x) as xx approaches a value cc is an indeterminate form 0/00/0 or /\infty/\infty, then the limit is the same as the limit of the derivatives of the numerator and the denominator, provided that the limit exists.
  4. Finding the derivatives: We will find the derivatives of the numerator and the denominator separately. The derivative of the numerator x+1x+1 with respect to xx is 11. The derivative of the denominator xex+exxe^{x}+e^{x} with respect to xx is ex+xex+exe^{x} + xe^{x} + e^{x} using the product rule and the fact that the derivative of exe^{x} is exe^{x}.
  5. Substituting x=1x = -1: Now we apply L'Hôpital's Rule:\newlinelimx1f(x)=limx11ex+xex+ex\lim_{x \to -1} f(x) = \lim_{x \to -1} \frac{1}{e^x + xe^x + e^x}
  6. Simplifying the expression: We substitute x=1x = -1 into the derivatives to find the limit: limx11ex+xex+ex=1e1+(1)e1+e1\lim_{x \to -1} \frac{1}{e^{x} + xe^{x} + e^{x}} = \frac{1}{e^{-1} + (-1)e^{-1} + e^{-1}}
  7. Final result: Simplify the expression:\newline(1)/(e1e1+e1)=(1)/(e1)(1)/(e^{-1} - e^{-1} + e^{-1}) = (1)/(e^{-1})
  8. Final result: Simplify the expression:\newline(1)/(e1e1+e1)=(1)/(e1)(1)/(e^{-1} - e^{-1} + e^{-1}) = (1)/(e^{-1})Since e1e^{-1} is the same as 1/e1/e, we can rewrite the expression as:\newline(1)/(1/e)=e(1)/(1/e) = e

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