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Worked Examples · Example 7

Q.Evaluate lim⁡x→0e3x−1x\lim_{x \to 0} \dfrac{e^{3x}-1}{x}.

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The standard limit lim⁡x→0ex−1x=1\lim_{x \to 0}\dfrac{e^x-1}{x}=1 applies only when the exponent of ee matches the denominator exactly — here the exponent is 3x3x while the denominator is only xx, so the expression must be rewritten first.

Multiply and divide by 33: e3x−1x=3×e3x−13x\dfrac{e^{3x}-1}{x} = 3 \times \dfrac{e^{3x}-1}{3x}

Substituting u=3xu=3x (so u→0u \to 0 as x→0x \to 0): lim⁡x→0e3x−13x=lim⁡u→0eu−1u=1\lim_{x \to 0} \dfrac{e^{3x}-1}{3x} = \lim_{u \to 0} \dfrac{e^{u}-1}{u} = 1

Therefore: lim⁡x→0e3x−1x=3×1=3\lim_{x \to 0} \dfrac{e^{3x}-1}{x} = 3 \times 1 = 3 …

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