Limit of \( \displaystyle \frac{- 2 x + e^{2 x} - 1}{4 x^{2}} \) as \( x \to 0 \)
Problem 1.81 · medium
Evaluate \( \displaystyle \lim_{x \to 0} \frac{- 2 x + e^{2 x} - 1}{4 x^{2}} \).
- \[ \lim_{x \to 0^+}\left(\frac{- 2 x + e^{2 x} - 1}{4 x^{2}}\right) \]limit algebraStarting with the original limit expression. Rearranging the terms in the numerator.✓ Proved
- \[ = \lim_{x \to 0^+}\left(\frac{\frac{d}{d x} \left(- 2 x + e^{2 x} - 1\right)}{\frac{d}{d x} 4 x^{2}}\right) \]lhopitalApplying L'Hopital's rule because the limit is of the form 0/0.✓ Proved
- \[ = \lim_{x \to 0^+}\left(\frac{2 e^{2 x} - 2}{8 x}\right) \]simplify factorComputing the derivatives in the numerator and denominator. Factoring out the constant 2 from the numerator.✓ Proved
- \[ = \lim_{x \to 0^+}\left(\frac{e^{2 x} - 1}{4 x}\right) \]simplifySimplifying the fraction by dividing the constants.✓ Proved
- \[ = \lim_{x \to 0^+}\left(\frac{\frac{d}{d x} \left(e^{2 x} - 1\right)}{\frac{d}{d x} 4 x}\right) \]lhopitalApplying L'Hopital's rule again as the limit is still 0/0.✓ Proved
- \[ = \lim_{x \to 0^+}\left(\frac{e^{2 x}}{2}\right) \]simplify simplifyComputing the derivatives. Simplifying the expression.✓ Proved
- \[ = \frac{1}{2} \]limitEvaluating the limit at x = 0.✓ Proved
- \[ = 0.5 \]simplifyFinal result.✓ Proved
Answer \( \frac{1}{2} \)
✓ Nihil obstat Every line of this solution was proved by the computer algebra system SymPy. The answer was also checked a second way, without looking at the solution. Reviewers found nothing wrong with the explanation.
The full receipt
| Line | Status | Checked by | Detail |
|---|---|---|---|
| 1 | ✓ Proved | sympy 1.14.0 | line 1 is the problem as stated |
| 2 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where x = 0 |
| 3 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where x = 0 undefined where Derivative(4*x**2, x) = 0 |
| 4 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where Derivative(4*x**2, x) = 0 undefined where x = 0 |
| 5 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where x = 0 |
| 6 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where x = 0 |
| 7 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where x = 0 undefined where Derivative(4*x, x) = 0 |
| 8 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where Derivative(4*x, x) = 0 |
| 9 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 |
| 10 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 |
| 11 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 |
| answer | ✓ Proved | sympy 1.14.0 | final line against the stated answer: simplify(a - b) reduced to 0 |
| answer, a second way | ✓ Proved | sympy 1.14.0 | SymPy took the limit from both sides and got the stated value |
Reviewers
gpt-oss:20b: passqwen3.6:27b-mlx: pass
Every verdict on record (4)
qwen3.6:27b-mlx: pass 2026-10-03gpt-oss:20b: pass 2026-10-03qwen3.6:27b-mlx: pass 2026-09-30gpt-oss:20b: pass 2026-09-30
Proved: SymPy reduced the difference between the two sides to zero. Checked independently: a separate
method, named above, confirmed it. Checked numerically: the two sides agree at every sampled point, which is evidence,
not proof. Reviewed: a model or a person read it; that is all a sentence can have. Solution by
gemma4:26b, checked 2026-10-03 with SymPy 1.14.0.