Limit of \( \displaystyle \frac{e^{3 x + 1} - 1}{3 x + 1} \) as \( x \to - \frac{1}{3} \)
Problem 1.430 · medium
Evaluate \( \displaystyle \lim_{x \to - \frac{1}{3}} \frac{e^{3 x + 1} - 1}{3 x + 1} \).
- \[ \lim_{x \to - \frac{1}{3}^+}\left(\frac{e^{3 x + 1} - 1}{3 x + 1}\right) \]limitStart with the limit of the function as x approaches -1/3 from the right.✓ Proved
- \[ = \lim_{x \to - \frac{1}{3}^+}\left(\frac{\frac{d}{d x} \left(e^{3 x + 1} - 1\right)}{\frac{d}{d x} \left(3 x + 1\right)}\right) \]lhopitalThe limit is an indeterminate form 0/0, so apply l'Hopital's rule.✓ Proved
- \[ = \lim_{x \to - \frac{1}{3}^+} e^{3 x + 1} \]simplify simplifyCalculate the derivatives of the numerator and denominator. Simplify the fraction by canceling the constant 3.✓ Proved
- \[ = 1 \]limit simplify simplifyEvaluate the limit by substituting x = -1/3. Simplify the exponent. Final evaluation.✓ Proved
Answer \( 1 \)
✓ 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 3*x + 1 = 0 undefined where Derivative(3*x + 1, x) = 0 |
| 3 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where Derivative(3*x + 1, x) = 0 |
| 4 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 |
| 5 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 |
| 6 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 |
| 7 | ✓ 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)
gpt-oss:20b: pass 2026-10-08qwen3.6:27b-mlx: pass 2026-10-08qwen3.6:27b-mlx: pass 2026-10-08 — The solution correctly applies l'Hopital's rule and simplifies the resulting expression. Each step changes only one aspect of the expression and uses valid labels from the fixed vocabulary.gpt-oss:20b: pass 2026-10-08
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 2026-10-08 with SymPy 1.14.0.