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Derivative of \( \displaystyle \frac{3 x^{2}}{4} + x - \left(\frac{3 x^{2}}{2} + 2 x + \frac{2}{3}\right) \ln{\left(3 x + 2 \right)} \)

Problem 2.1913 · hard

Differentiate \( \displaystyle f(x) = \frac{3 x^{2}}{4} + x - \left(\frac{3 x^{2}}{2} + 2 x + \frac{2}{3}\right) \ln{\left(3 x + 2 \right)} \).
  1. \[ \frac{d}{d x} \left(\frac{3 x^{2}}{4} + x - \left(\frac{3 x^{2}}{2} + 2 x + \frac{2}{3}\right) \ln{\left(3 x + 2 \right)}\right) \]
    Differentiate the function with respect to x.✓ Proved
  2. \[ = \frac{d}{d x} x + \frac{d}{d x} \frac{3 x^{2}}{4} - \frac{d}{d x} \left(\frac{3 x^{2}}{2} + 2 x + \frac{2}{3}\right) \ln{\left(3 x + 2 \right)} \]
    sumApply the sum rule.✓ Proved
  3. \[ = - \left(\frac{3 x^{2}}{2} + 2 x + \frac{2}{3}\right) \frac{d}{d x} \ln{\left(3 x + 2 \right)} - \ln{\left(3 x + 2 \right)} \frac{d}{d x} \left(\frac{3 x^{2}}{2} + 2 x + \frac{2}{3}\right) + \frac{d}{d x} x + \frac{d}{d x} \frac{3 x^{2}}{4} \]
    productApply the product rule to the third term.✓ Proved
  4. \[ = - \left(\frac{3 x^{2}}{2} + 2 x + \frac{2}{3}\right) \frac{d}{d x} \ln{\left(3 x + 2 \right)} - \left(\frac{d}{d x} \frac{2}{3} + \frac{d}{d x} 2 x + \frac{d}{d x} \frac{3 x^{2}}{2}\right) \ln{\left(3 x + 2 \right)} + \frac{d}{d x} x + \frac{d}{d x} \frac{3 x^{2}}{4} \]
    sumApply the sum rule to the first part of the product rule.✓ Proved
  5. \[ = - \left(\frac{d}{d x} 2 x + \frac{d}{d x} \frac{3 x^{2}}{2}\right) \ln{\left(3 x + 2 \right)} - \left(\frac{3 x^{2}}{2} + 2 x + \frac{2}{3}\right) \frac{d}{d x} \ln{\left(3 x + 2 \right)} + \frac{d}{d x} x + \frac{d}{d x} \frac{3 x^{2}}{4} \]
    constant algebraThe derivative of the constant 2/3 is 0. Simplify the expression inside the parentheses.✓ Proved
  6. \[ = - \left(3 x + 2\right) \ln{\left(3 x + 2 \right)} - \left(\frac{3 x^{2}}{2} + 2 x + \frac{2}{3}\right) \frac{d}{d x} \ln{\left(3 x + 2 \right)} + \frac{d}{d x} x + \frac{d}{d x} \frac{3 x^{2}}{4} \]
    power algebraApply the power rule to the derivatives of the polynomial terms. Simplify the polynomial derivative.✓ Proved
  7. \[ = - \left(3 x + 2\right) \ln{\left(3 x + 2 \right)} + \frac{d}{d x} x + \frac{d}{d x} \frac{3 x^{2}}{4} - \frac{\left(\frac{3 x^{2}}{2} + 2 x + \frac{2}{3}\right) \frac{d}{d x} \left(3 x + 2\right)}{3 x + 2} \]
    logarithmicApply the chain rule to the derivative of the logarithm.✓ Proved
  8. \[ = - \left(3 x + 2\right) \ln{\left(3 x + 2 \right)} + \frac{d}{d x} x + \frac{d}{d x} \frac{3 x^{2}}{4} - \frac{3 \left(\frac{3 x^{2}}{2} + 2 x + \frac{2}{3}\right)}{3 x + 2} \]
    chainApply the chain rule to the derivative of 3*x + 2.✓ Proved
  9. \[ = - \left(3 x + 2\right) \ln{\left(3 x + 2 \right)} + \frac{d}{d x} x + \frac{d}{d x} \frac{3 x^{2}}{4} - \frac{\frac{9 x^{2}}{2} + 6 x + 2}{3 x + 2} \]
    algebra algebraMultiply the constant 3 into the numerator. Distribute the 3 into the polynomial.✓ Proved
  10. \[ = \frac{3 x}{2} - \left(3 x + 2\right) \ln{\left(3 x + 2 \right)} + 1 - \frac{\frac{9 x^{2}}{2} + 6 x + 2}{3 x + 2} \]
    power algebra algebra algebra simplifyEvaluate the derivatives of the first two terms. Simplify the first term. Distribute the negative sign. Note that the fraction can be simplified further if needed, but let's check the final form. Final simplification of the expression.✓ Proved
Answer \( \left(- 3 x - 2\right) \ln{\left(3 x + 2 \right)} \)

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
log is undefined for non-positive arguments
3✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
log is undefined for non-positive arguments
4✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
log is undefined for non-positive arguments
5✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
log is undefined for non-positive arguments
6✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
log is undefined for non-positive arguments
7✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
log is undefined for non-positive arguments
8✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
log is undefined for non-positive arguments
9✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
log is undefined for non-positive arguments
undefined where 3*x + 2 = 0
10✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
log is undefined for non-positive arguments
undefined where 3*x + 2 = 0
11✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
log is undefined for non-positive arguments
undefined where 3*x + 2 = 0
12✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
log is undefined for non-positive arguments
undefined where 3*x + 2 = 0
13✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
log is undefined for non-positive arguments
undefined where 3*x + 2 = 0
14✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
log is undefined for non-positive arguments
undefined where 3*x + 2 = 0
15✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
log is undefined for non-positive arguments
undefined where 3*x + 2 = 0
16✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
log is undefined for non-positive arguments
undefined where 3*x + 2 = 0
17✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
log is undefined for non-positive arguments
undefined where 3*x + 2 = 0
answer✓ Provedsympy 1.14.0final line against the stated answer: simplify(a - b) reduced to 0
log is undefined for non-positive arguments
answer, a second way✓ Provedsympy 1.14.0SymPy differentiated f directly and got the stated answer

Reviewers

  • gpt-oss:20b: fail (error) — Step 7 applies both the power rule (to 3*x**2/2) and the constant rule (to 2*x) in a single line, violating the one‑rule‑per‑step rule. Step 13 similarly combines the power rule for 3*x**2/4 and the constant rule for x in one step.
  • qwen3.6:27b-mlx: fail (error) — The solution fails to simplify the rational term (9*x**2/2 + 6*x + 2)/(3*x + 2) to 3*x/2 + 2, which is necessary to cancel the 3/2*x + 1 terms and arrive at the stated answer. Consequently, the final line is algebraically unequal to the stated answer.
Every verdict on record (4)
  • gpt-oss:20b: fail (error) 2026-10-09 — Step 7 applies both the power rule (to 3*x**2/2) and the constant rule (to 2*x) in a single line, violating the one‑rule‑per‑step rule. Step 13 similarly combines the power rule for 3*x**2/4 and the constant rule for x in one step.
  • qwen3.6:27b-mlx: fail (error) 2026-10-09 — The solution fails to simplify the rational term (9*x**2/2 + 6*x + 2)/(3*x + 2) to 3*x/2 + 2, which is necessary to cancel the 3/2*x + 1 terms and arrive at the stated answer. Consequently, the final line is algebraically unequal to the stated answer.
  • gpt-oss:20b: pass 2026-10-09
  • qwen3.6:27b-mlx: fail (misleading) 2026-10-09 — Step 9 is labeled 'logarithmic' but the note describes applying the chain rule; the step actually applies the chain rule to the logarithm, so the label should be 'chain'. Furthermore, the solution fails to simplify the rational term (9*x**2/2 + 6*x + 2)/(3*x + 2) to 3*x/2 + 2, leaving the final answer in an unsimplified form that does not match the stated answer.

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 2026-10-09 with SymPy 1.14.0.