Derivative of \( \displaystyle \left(x + \frac{1}{5}\right) e^{5 x + 2} \)
Problem 2.1295 · medium
Differentiate \( \displaystyle f(x) = \left(x + \frac{1}{5}\right) e^{5 x + 2} \).
- \[ \frac{d}{d x} \left(x + \frac{1}{5}\right) e^{5 x + 2} \]derivativeStart with the derivative of the function.✓ Proved
- \[ = \frac{d}{d x} x e^{5 x + 2} + \frac{d}{d x} \frac{e^{5 x + 2}}{5} \]sumApply the sum rule.✓ Proved
- \[ = \frac{d}{d x} x e^{5 x + 2} + \frac{\frac{d}{d x} e^{5 x + 2}}{5} \]constant-multipleApply the constant multiple rule to the second term.✓ Proved
- \[ = x \frac{d}{d x} e^{5 x + 2} + e^{5 x + 2} \frac{d}{d x} x + \frac{\frac{d}{d x} e^{5 x + 2}}{5} \]productApply the product rule to the first term.✓ Proved
- \[ = x \frac{d}{d x} e^{5 x + 2} + e^{5 x + 2} + \frac{\frac{d}{d x} e^{5 x + 2}}{5} \]derivativeDifferentiate the first part of the product rule.✓ Proved
- \[ = x e^{5 x + 2} \frac{d}{d x} \left(5 x + 2\right) + e^{5 x + 2} + \frac{\frac{d}{d x} e^{5 x + 2}}{5} \]productApply the product rule to the second term.✓ Proved
- \[ = 5 x e^{5 x + 2} + e^{5 x + 2} + \frac{\frac{d}{d x} e^{5 x + 2}}{5} \]derivativeDifferentiate the inner function 5*x + 2.✓ Proved
- \[ = 5 x e^{5 x + 2} + \frac{e^{5 x + 2} \frac{d}{d x} \left(5 x + 2\right)}{5} + e^{5 x + 2} \]algebraRearrange the terms.✓ Proved
- \[ = 5 x e^{5 x + 2} + 2 e^{5 x + 2} \]derivative algebra algebraDifferentiate the inner function again. Simplify the constant multiplication. Combine like terms.✓ Proved
- \[ = \left(5 x + 2\right) e^{5 x + 2} \]algebraFactor out the common exponential term.✓ Proved
Answer \( \left(5 x + 2\right) e^{5 x + 2} \)
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. A reviewer's objection to the explanation stands; see the receipt.
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 |
| 10 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 |
| 11 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 |
| 12 | ✓ 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: fail (error) — Step 9 incorrectly applies a derivative to the term (1/5)*exp(5*x+2)*Derivative(5*x+2,x). That term should have been simplified to (1/5)*exp(5*x+2)*5 in step 7, not differentiated again. This violates the rule that each step changes only one thing and mislabels the operation.qwen3.6:27b-mlx: fail (error) — Step 6 is labeled 'product' but applies the chain rule to differentiate exp(5*x + 2). Step 8 is labeled 'algebra' but applies the chain rule to the third term. These steps mix rules or mislabel the chain rule application.
Every verdict on record (4)
qwen3.6:27b-mlx: fail (error) 2026-10-03 — Step 6 is labeled 'product' but applies the chain rule to differentiate exp(5*x + 2). Step 8 is labeled 'algebra' but applies the chain rule to the third term. These steps mix rules or mislabel the chain rule application.gpt-oss:20b: fail (error) 2026-10-03 — Step 9 incorrectly applies a derivative to the term (1/5)*exp(5*x+2)*Derivative(5*x+2,x). That term should have been simplified to (1/5)*exp(5*x+2)*5 in step 7, not differentiated again. This violates the rule that each step changes only one thing and mislabels the operation.qwen3.6:27b-mlx: fail (error) 2026-09-30 — Step 6 is labeled 'product' but applies the chain rule to differentiate the exponential function. Step 8 is labeled 'algebra' but performs differentiation (chain rule) on the third term, which is a mathematical error in labeling and logic.gpt-oss:20b: fail (error) 2026-09-30 — Step 6 incorrectly applies the product rule to the derivative of exp(5*x+2); it should use the chain rule. Subsequent steps double‑count the derivative of the inner function, leading to an incorrect final expression.
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 2026-10-03 with SymPy 1.14.0.