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Derivative of \( \displaystyle \left(- x - \frac{1}{2}\right) e^{2 x + 2} \)

Problem 2.884 · medium

Differentiate \( \displaystyle f(x) = \left(- x - \frac{1}{2}\right) e^{2 x + 2} \).
  1. \[ \frac{d}{d x} \left(- x - \frac{1}{2}\right) e^{2 x + 2} \]
    derivativeStart with the derivative of the function.✓ Proved
  2. \[ = \left(- x - \frac{1}{2}\right) \frac{d}{d x} e^{2 x + 2} + e^{2 x + 2} \frac{d}{d x} \left(- x - \frac{1}{2}\right) \]
    productApply the product rule.✓ Proved
  3. \[ = \left(- x - \frac{1}{2}\right) \frac{d}{d x} e^{2 x + 2} + e^{2 x + 2} \frac{d}{d x} \left(- \frac{1}{2}\right) + e^{2 x + 2} \frac{d}{d x} \left(- x\right) \]
    sumApply the sum rule to the first term.✓ Proved
  4. \[ = \left(- x - \frac{1}{2}\right) \frac{d}{d x} e^{2 x + 2} - e^{2 x + 2} \]
    derivativeDifferentiate the individual terms.✓ Proved
  5. \[ = - \left(x + \frac{1}{2}\right) \frac{d}{d x} e^{2 x + 2} - e^{2 x + 2} \]
    algebraSimplify the expression.✓ Proved
  6. \[ = - \left(x + \frac{1}{2}\right) e^{2 x + 2} \frac{d}{d x} \left(2 x + 2\right) - e^{2 x + 2} \]
    exponentialDifferentiate the exponential term using the chain rule.✓ Proved
  7. \[ = - 2 \left(x + \frac{1}{2}\right) e^{2 x + 2} - e^{2 x + 2} \]
    derivativeDifferentiate the exponent.✓ Proved
  8. \[ = - \left(2 x + 1\right) e^{2 x + 2} - e^{2 x + 2} \]
    algebraDistribute the constant and simplify.✓ Proved
  9. \[ = - 2 x e^{2 x + 2} - 2 e^{2 x + 2} \]
    algebra algebraDistribute the term. Combine like terms.✓ Proved
  10. \[ = \left(- 2 x - 2\right) e^{2 x + 2} \]
    simplifyFactor out the common term.✓ Proved
Answer \( 2 \left(- x - 1\right) e^{2 x + 2} \)

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. The reviewers disagree about how one step is explained; every verdict is in the receipt.

The full receipt
LineStatusChecked byDetail
1✓ Provedsympy 1.14.0line 1 is the problem as stated
2✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
3✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
4✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
5✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
6✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
7✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
8✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
9✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
10✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
11✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
answer✓ Provedsympy 1.14.0final line against the stated answer: simplify(a - b) reduced to 0
answer, a second way✓ Provedsympy 1.14.0SymPy differentiated f directly and got the stated answer

Reviewers

  • gpt-oss:20b: pass
  • qwen3.6:27b-mlx: fail (error) — Step 5 incorrectly changes the sign of the third term from positive to negative (from `+ (-x - 1/2)*...` to `- (x + 1/2)*...`) without justification, effectively applying an algebraic simplification to one term while dropping the sign change logic or misapplying it. Additionally, Step 6 labels the application of the chain rule as 'exponential', which is not in the allowed vocabulary for that specific structural change (though 'chain' is allowed, the step also performs the differentiation of the inner function in step 7, making step 6 a partial application that is confusingly labeled).
Every verdict on record (4)
  • qwen3.6:27b-mlx: fail (error) 2026-09-26 — Step 5 incorrectly changes the sign of the third term from positive to negative (from `+ (-x - 1/2)*...` to `- (x + 1/2)*...`) without justification, effectively applying an algebraic simplification to one term while dropping the sign change logic or misapplying it. Additionally, Step 6 labels the application of the chain rule as 'exponential', which is not in the allowed vocabulary for that specific structural change (though 'chain' is allowed, the step also performs the differentiation of the inner function in step 7, making step 6 a partial application that is confusingly labeled).
  • gpt-oss:20b: pass 2026-09-26
  • qwen3.6:27b-mlx: fail (error) 2026-09-26 — Step 5 incorrectly changes the sign of the term `(-x - 1/2)` to `-(x + 1/2)` while simultaneously dropping the `Derivative` operator, applying two distinct operations (algebraic simplification and differentiation) in a single step. Additionally, Step 6 is labeled 'exponential' but describes using the chain rule, which is a mislabeling defect.
  • gpt-oss:20b: pass 2026-09-26

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 2026-09-26 with SymPy 1.14.0.