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Derivative of \( \displaystyle 5 x e^{4 x + 1} \)

Problem 2.94 · hard

Differentiate \( \displaystyle f(x) = 5 x e^{4 x + 1} \).
  1. \[ \frac{d}{d x} 5 x e^{4 x + 1} \]
    derivativeStart with the derivative of the function.✓ Proved
  2. \[ = 5 \frac{d}{d x} x e^{4 x + 1} \]
    constant-multiplePull out the constant factor 5.✓ Proved
  3. \[ = 5 x \frac{d}{d x} e^{4 x + 1} + 5 e^{4 x + 1} \frac{d}{d x} x \]
    productApply the product rule to the remaining term.✓ Proved
  4. \[ = 5 x \frac{d}{d x} e^{4 x + 1} + 5 e^{4 x + 1} \]
    derivativeDifferentiate x.✓ Proved
  5. \[ = 5 x e^{4 x + 1} \frac{d}{d x} \left(4 x + 1\right) + 5 e^{4 x + 1} \]
    chainApply the chain rule to the exponential term.✓ Proved
  6. \[ = 20 x e^{4 x + 1} + 5 e^{4 x + 1} \]
    derivative algebraDifferentiate the inner function 4*x + 1. Rearrange the terms.✓ Proved
  7. \[ = 5 \left(4 x + 1\right) e^{4 x + 1} \]
    simplifyFactor out the common exponential term.✓ Proved
Answer \( \left(20 x + 5\right) e^{4 x + 1} \)

✓ 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
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
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
  • deepseek-r1:70b: pass
  • qwen3.6:27b-mlx: pass
Every verdict on record (12)
  • qwen3.6:27b-mlx: pass 2026-09-20
  • gpt-oss:20b: pass 2026-09-20
  • qwen3.6:27b-mlx: pass 2026-09-20
  • gpt-oss:20b: pass 2026-09-20
  • qwen3.6:27b-mlx: pass 2026-09-19
  • deepseek-r1:70b: pass 2026-09-19
  • gpt-oss:20b: pass 2026-09-19
  • qwen3.6:27b-mlx: pass 2026-09-19 — The solution correctly applies the constant multiple, product, and chain rules in separate steps. The labels accurately reflect the operations performed, and the algebraic simplifications are sound.
  • deepseek-r1:70b: pass 2026-09-19
  • gpt-oss:20b: pass 2026-09-19
  • gpt-oss:20b: pass 2026-09-17
  • deepseek-r1:70b: pass 2026-09-17

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.