∫Calc Practice

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

Problem 2.2107 · hard

Differentiate \( \displaystyle f(x) = - x + \ln{\left(\left(3 x\right)^{x} \right)} \).
  1. \[ \frac{d}{d x} \left(- x + \ln{\left(\left(3 x\right)^{x} \right)}\right) \]
    derivativeStart with the derivative of the function.✓ Proved
  2. \[ = \frac{d}{d x} \left(- x\right) + \frac{d}{d x} \ln{\left(\left(3 x\right)^{x} \right)} \]
    sumApply the sum rule.✓ Proved
  3. \[ = \frac{d}{d x} \left(- x\right) + \frac{d}{d x} \ln{\left(e^{x \ln{\left(3 x \right)}} \right)} \]
    rewriteRewrite the logarithm using the exponential identity.✓ Proved
  4. \[ = \frac{d}{d x} \left(- x\right) + \frac{d}{d x} x \ln{\left(3 x \right)} \]
    simplifySimplify the logarithm of the exponential.✓ Proved
  5. \[ = \frac{d}{d x} \left(- x\right) + \frac{d}{d x} x \left(\ln{\left(x \right)} + \ln{\left(3 \right)}\right) \]
    algebraExpand the logarithm of the product.✓ Proved
  6. \[ = x \frac{d}{d x} \left(\ln{\left(x \right)} + \ln{\left(3 \right)}\right) + \left(\ln{\left(x \right)} + \ln{\left(3 \right)}\right) \frac{d}{d x} x + \frac{d}{d x} \left(- x\right) \]
    productApply the product rule.✓ Proved
  7. \[ = x \frac{d}{d x} \left(\ln{\left(x \right)} + \ln{\left(3 \right)}\right) + \ln{\left(x \right)} + \frac{d}{d x} \left(- x\right) + \ln{\left(3 \right)} \]
    derivative algebraDifferentiate x. Simplify the expression.✓ Proved
  8. \[ = x \left(\frac{d}{d x} \ln{\left(3 \right)} + \frac{d}{d x} \ln{\left(x \right)}\right) + \ln{\left(x \right)} + \frac{d}{d x} \left(- x\right) + \ln{\left(3 \right)} \]
    sumApply the sum rule to the derivative.✓ Proved
  9. \[ = x \frac{d}{d x} \ln{\left(x \right)} + \ln{\left(x \right)} + \frac{d}{d x} \left(- x\right) + \ln{\left(3 \right)} \]
    derivativeDifferentiate the constant log(3).✓ Proved
  10. \[ = \ln{\left(x \right)} + \frac{d}{d x} \left(- x\right) + 1 + \ln{\left(3 \right)} \]
    derivative algebraDifferentiate log(x). Simplify the expression.✓ Proved
  11. \[ = \ln{\left(x \right)} + \ln{\left(3 \right)} \]
    derivative simplifyDifferentiate -x. Combine terms and simplify.✓ Proved
Answer \( \ln{\left(3 x \right)} \)

✓ 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
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
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)
  • qwen3.6:27b-mlx: pass 2026-10-12
  • gpt-oss:20b: pass 2026-10-12
  • qwen3.6:27b-mlx: pass 2026-10-12 — 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 2026-10-12

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 2026-10-12 with SymPy 1.14.0.