Limit of \( \displaystyle \frac{- x + e^{x + 1} - 2}{\left(x + 1\right)^{2}} \) as \( x \to -1 \)
Problem 1.376 · medium
Evaluate \( \displaystyle \lim_{x \to -1} \frac{- x + e^{x + 1} - 2}{\left(x + 1\right)^{2}} \).
- \[ \lim_{x \to -1^+}\left(\frac{- x + e^{x + 1} - 2}{\left(x + 1\right)^{2}}\right) \]limit algebraStart with the limit of the given function. Rewrite the numerator to group terms with (x + 1).✓ Proved
- \[ = \lim_{x \to -1^+}\left(\frac{\frac{d}{d x} \left(- x + e^{x + 1} - 2\right)}{\frac{d}{d x} \left(x + 1\right)^{2}}\right) \]lhopitalApply L'Hopital's rule since the limit is in the form 0/0.✓ Proved
- \[ = \lim_{x \to -1^+}\left(\frac{e^{x + 1} - 1}{2 x + 2}\right) \]simplifyCompute the derivatives in the numerator and denominator.✓ Proved
- \[ = \lim_{x \to -1^+}\left(\frac{\frac{d}{d x} \left(e^{x + 1} - 1\right)}{\frac{d}{d x} \left(2 x + 2\right)}\right) \]lhopitalApply L'Hopital's rule again since the limit is in the form 0/0.✓ Proved
- \[ = \lim_{x \to -1^+}\left(\frac{e^{x + 1}}{2}\right) \]simplifyCompute the derivatives.✓ Proved
- \[ = \frac{1}{2} \]limit simplifyEvaluate the limit by substituting x = -1. Simplify the final value.✓ 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 + 1 = 0 |
| 3 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where x + 1 = 0 undefined where Derivative((x + 1)**2, x) = 0 |
| 4 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where Derivative((x + 1)**2, x) = 0 undefined where 2*x + 2 = 0 |
| 5 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where 2*x + 2 = 0 undefined where Derivative(2*x + 2, x) = 0 |
| 6 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where Derivative(2*x + 2, x) = 0 |
| 7 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 |
| 8 | ✓ 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 2026-10-07qwen3.6:27b-mlx: pass 2026-10-07qwen3.6:27b-mlx: pass 2026-10-07 — The solution correctly applies L'Hôpital's rule twice and simplifies the resulting expressions. Each step changes only one aspect of the expression and uses valid labels from the fixed vocabulary.gpt-oss:20b: pass 2026-10-07
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 2026-10-07 with SymPy 1.14.0.