We need to find the limit of the function $\frac{e^x + 2x - 1}{2e^x + 1}$ as $x$ approaches infinity.

AnalysisLimitsL'Hopital's RuleExponential FunctionsCalculus
2025/4/26

1. Problem Description

We need to find the limit of the function ex+2x12ex+1\frac{e^x + 2x - 1}{2e^x + 1} as xx approaches infinity.

2. Solution Steps

We are given the limit:
\lim_{x \to \infty} \frac{e^x + 2x - 1}{2e^x + 1}
As xx approaches infinity, exe^x also approaches infinity. Both the numerator and denominator approach infinity, so we have an indeterminate form of type \frac{\infty}{\infty}. We can apply L'Hopital's Rule. L'Hopital's Rule states that if limxcf(x)g(x)\lim_{x \to c} \frac{f(x)}{g(x)} is of the form 00\frac{0}{0} or \frac{\infty}{\infty}, then limxcf(x)g(x)=limxcf(x)g(x)\lim_{x \to c} \frac{f(x)}{g(x)} = \lim_{x \to c} \frac{f'(x)}{g'(x)}, provided the limit on the right exists.
First, we find the derivatives of the numerator and the denominator:
\frac{d}{dx}(e^x + 2x - 1) = e^x + 2
\frac{d}{dx}(2e^x + 1) = 2e^x
So, applying L'Hopital's Rule once, we get:
\lim_{x \to \infty} \frac{e^x + 2x - 1}{2e^x + 1} = \lim_{x \to \infty} \frac{e^x + 2}{2e^x}
This is still of the form \frac{\infty}{\infty}, so we can apply L'Hopital's Rule again.
\frac{d}{dx}(e^x + 2) = e^x
\frac{d}{dx}(2e^x) = 2e^x
So, applying L'Hopital's Rule a second time, we get:
\lim_{x \to \infty} \frac{e^x + 2}{2e^x} = \lim_{x \to \infty} \frac{e^x}{2e^x}
We can simplify the fraction:
\lim_{x \to \infty} \frac{e^x}{2e^x} = \lim_{x \to \infty} \frac{1}{2} = \frac{1}{2}
Alternatively, we can divide the numerator and denominator by exe^x from the beginning:
\lim_{x \to \infty} \frac{e^x + 2x - 1}{2e^x + 1} = \lim_{x \to \infty} \frac{1 + \frac{2x}{e^x} - \frac{1}{e^x}}{2 + \frac{1}{e^x}}
As xx \to \infty, 1ex0\frac{1}{e^x} \to 0. Also, limx2xex=0\lim_{x \to \infty} \frac{2x}{e^x} = 0 by L'Hopital's Rule (since limx2ex=0\lim_{x \to \infty} \frac{2}{e^x} = 0).
\lim_{x \to \infty} \frac{1 + \frac{2x}{e^x} - \frac{1}{e^x}}{2 + \frac{1}{e^x}} = \frac{1 + 0 - 0}{2 + 0} = \frac{1}{2}

3. Final Answer

12\frac{1}{2}

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