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Home›Calculus 1›Product rule›Problem 2.1577

Derivative of \( \displaystyle - \frac{x^{2}}{4} + \frac{3 x}{2} + \left(\frac{x^{2}}{2} - 3 x + \frac{9}{2}\right) \ln{\left(x - 3 \right)} \)

Problem 2.1577 · hard

Differentiate \( \displaystyle f(x) = - \frac{x^{2}}{4} + \frac{3 x}{2} + \left(\frac{x^{2}}{2} - 3 x + \frac{9}{2}\right) \ln{\left(x - 3 \right)} \).
  1. \[ \frac{d}{d x} \left(- \frac{x^{2}}{4} + \frac{3 x}{2} + \left(\frac{x^{2}}{2} - 3 x + \frac{9}{2}\right) \ln{\left(x - 3 \right)}\right) \]
    Start with the derivative of the function.✓ Proved
  2. \[ = \frac{d}{d x} \frac{3 x}{2} + \frac{d}{d x} \left(- \frac{x^{2}}{4}\right) + \frac{d}{d x} \left(\frac{x^{2}}{2} - 3 x + \frac{9}{2}\right) \ln{\left(x - 3 \right)} \]
    sumApply the sum rule.✓ Proved
  3. \[ = \left(\frac{x^{2}}{2} - 3 x + \frac{9}{2}\right) \frac{d}{d x} \ln{\left(x - 3 \right)} + \ln{\left(x - 3 \right)} \frac{d}{d x} \left(\frac{x^{2}}{2} - 3 x + \frac{9}{2}\right) + \frac{d}{d x} \frac{3 x}{2} + \frac{d}{d x} \left(- \frac{x^{2}}{4}\right) \]
    productApply the product rule to the third term.✓ Proved
  4. \[ = \left(x - 3\right) \ln{\left(x - 3 \right)} + \left(\frac{x^{2}}{2} - 3 x + \frac{9}{2}\right) \frac{d}{d x} \ln{\left(x - 3 \right)} + \frac{d}{d x} \frac{3 x}{2} + \frac{d}{d x} \left(- \frac{x^{2}}{4}\right) \]
    derivative algebraDifferentiate the polynomial part of the product. Simplify the polynomial term.✓ Proved
  5. \[ = \left(x - 3\right) \ln{\left(x - 3 \right)} + \frac{d}{d x} \frac{3 x}{2} + \frac{d}{d x} \left(- \frac{x^{2}}{4}\right) + \frac{\frac{x^{2}}{2} - 3 x + \frac{9}{2}}{x - 3} \]
    derivativeDifferentiate the logarithm.✓ Proved
  6. \[ = - \frac{x}{2} + \left(x - 3\right) \ln{\left(x - 3 \right)} + \frac{3}{2} + \frac{\frac{x^{2}}{2} - 3 x + \frac{9}{2}}{x - 3} \]
    derivative algebraEvaluate the derivatives of the power and linear terms. Simplify the first term.✓ Proved
  7. \[ = - \frac{x}{2} + \left(x - 3\right) \ln{\left(x - 3 \right)} + \frac{3}{2} + \frac{0.5 x^{2} - 3 x + 4.5}{x - 3} \]
    algebraRewrite coefficients for clarity.✓ Proved
  8. \[ = - \frac{x}{2} + \left(x - 3\right) \ln{\left(x - 3 \right)} + \frac{3}{2} + \frac{0.5 x^{2} - 3.0 x + 4.5}{x - 3} \]
    algebraFactor out 0.5 from the numerator.✓ Proved
  9. \[ = \left(x - 3\right) \ln{\left(x - 3 \right)} \]
    algebra algebra algebra algebra algebra simplifyFactor the quadratic expression. Cancel the common factor (x - 3). Distribute the 0.5. Convert 1.5 to a fraction. Group like terms. Combine all terms to get the final result.✓ Proved
Answer \( \left(x - 3\right) \ln{\left(x - 3 \right)} \)

✓ 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
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
undefined where x - 3 = 0
7✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
log is undefined for non-positive arguments
undefined where x - 3 = 0
8✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
log is undefined for non-positive arguments
undefined where x - 3 = 0
9✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
log is undefined for non-positive arguments
undefined where x - 3 = 0
10✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
log is undefined for non-positive arguments
undefined where x - 3 = 0
11✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
log is undefined for non-positive arguments
undefined where x - 3 = 0
12✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
log is undefined for non-positive arguments
13✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
log is undefined for non-positive arguments
14✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
log is undefined for non-positive arguments
15✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
log is undefined for non-positive arguments
16✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
log is undefined for non-positive arguments
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: pass
  • qwen3.6:27b-mlx: pass — The solution correctly applies differentiation rules and algebraic simplifications. Each step adheres to the single-change constraint and uses valid labels from the provided vocabulary.
Every verdict on record (4)
  • qwen3.6:27b-mlx: pass 2026-10-05 — The solution correctly applies differentiation rules and algebraic simplifications. Each step adheres to the single-change constraint and uses valid labels from the provided vocabulary.
  • gpt-oss:20b: pass 2026-10-05
  • qwen3.6:27b-mlx: pass 2026-10-05 — The solution correctly applies differentiation rules and algebraic simplifications. Each step adheres to the single-change constraint and uses valid labels from the fixed vocabulary.
  • gpt-oss:20b: fail (style) 2026-10-05 — Step 7 applies the derivative to two separate terms in one step but labels it only as "derivative". According to the contract, each step must change only one thing; this step changes two terms simultaneously and should be split into separate derivative steps or labeled with the sum rule.

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 2026-10-05 with SymPy 1.14.0.