Derivative of \( \displaystyle 3 x e^{3 x + 1} \)
Problem 2.390 · medium
Differentiate \( \displaystyle f(x) = 3 x e^{3 x + 1} \).
- \[ \frac{d}{d x} 3 x e^{3 x + 1} \]derivativeStart with the derivative of the function.✓ Proved
- \[ = 3 \frac{d}{d x} x e^{3 x + 1} \]constant-multiplePull out the constant factor 3.✓ Proved
- \[ = 3 x \frac{d}{d x} e^{3 x + 1} + 3 e^{3 x + 1} \frac{d}{d x} x \]productApply the product rule to the remaining terms.✓ Proved
- \[ = 3 x \frac{d}{d x} e^{3 x + 1} + 3 e^{3 x + 1} \]derivativeDifferentiate the first part of the product.✓ Proved
- \[ = 3 x e^{3 x + 1} \frac{d}{d x} \left(3 x + 1\right) + 3 e^{3 x + 1} \]chainApply the chain rule to the exponential term.✓ Proved
- \[ = 9 x e^{3 x + 1} + 3 e^{3 x + 1} \]derivative algebra algebraDifferentiate the inner function 3*x + 1. Simplify the expression inside the parentheses. Distribute the 3.✓ Proved
- \[ = 3 \left(3 x + 1\right) e^{3 x + 1} \]simplifyFactor out the common term.✓ Proved
Answer \( \left(9 x + 3\right) e^{3 x + 1} \)
✓ 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
| 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 |
| 3 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 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 |
| 8 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 |
| 9 | ✓ 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 differentiated f directly and got the stated answer |
Reviewers
gpt-oss:20b: passqwen3.6:27b-mlx: pass — The solution correctly applies differentiation rules in a step-by-step manner, adhering to the one-change-per-step constraint and using valid labels from the fixed vocabulary.
Every verdict on record (6)
qwen3.6:27b-mlx: pass 2026-09-21 — The solution correctly applies differentiation rules in a step-by-step manner, adhering to the one-change-per-step constraint and using valid labels from the fixed vocabulary.gpt-oss:20b: pass 2026-09-21qwen3.6:27b-mlx: pass 2026-09-20 — The solution correctly applies the constant multiple, product, and chain rules in separate steps. All labels are valid and the algebraic simplifications are sound.gpt-oss:20b: pass 2026-09-20qwen3.6:27b-mlx: pass 2026-09-20 — The solution correctly applies the constant multiple, product, and chain rules in separate steps. The labels accurately reflect the operations performed, and the final simplification is algebraically sound.gpt-oss:20b: pass 2026-09-20
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.