∫Calc Practice

Derivative of \( \displaystyle 3 x \ln{\left(x \right)} - 3 x \)

Problem 2.1937 · hard Beautiful

Differentiate \( \displaystyle f(x) = 3 x \ln{\left(x \right)} - 3 x \).
  1. \[ \frac{d}{d x} \left(3 x \ln{\left(x \right)} - 3 x\right) \]
    derivativeStart with the derivative of the function.✓ Proved
  2. \[ = - \frac{d}{d x} 3 x + \frac{d}{d x} 3 x \ln{\left(x \right)} \]
    sumApply the sum rule.✓ Proved
  3. \[ = - \frac{d}{d x} 3 x + 3 \frac{d}{d x} x \ln{\left(x \right)} \]
    constant-multipleFactor out the constant 3.✓ Proved
  4. \[ = 3 x \frac{d}{d x} \ln{\left(x \right)} + 3 \ln{\left(x \right)} \frac{d}{d x} x - \frac{d}{d x} 3 x \]
    productApply the product rule to the first term.✓ Proved
  5. \[ = 3 \ln{\left(x \right)} - \frac{d}{d x} 3 x + 3 \]
    derivative algebra algebraDifferentiate the individual components. Simplify the expression inside the parentheses. Distribute the 3 into the parentheses.✓ Proved
  6. \[ = 3 \ln{\left(x \right)} - 3 \frac{d}{d x} x + 3 \]
    constant-multipleFactor out the 3 from the second term.✓ Proved
  7. \[ = 3 \ln{\left(x \right)} \]
    derivative algebra simplifyDifferentiate the remaining term. Simplify the expression. Combine the constant terms.✓ Proved
Answer \( 3 \ln{\left(x \right)} \)

✓ 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
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
10✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
log is undefined for non-positive arguments
11✓ 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
Every verdict on record (4)
  • gpt-oss:20b: pass 2026-10-09
  • qwen3.6:27b-mlx: pass 2026-10-09
  • qwen3.6:27b-mlx: pass 2026-10-09 — The solution correctly applies differentiation rules step-by-step, adhering to the one-change-per-step constraint and using valid labels from the fixed vocabulary.
  • gpt-oss:20b: pass 2026-10-09

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.