∫Calc Practice

Derivative of \( \displaystyle 2 x \ln{\left(4 x + 2 \right)} - 2 x + \ln{\left(2 x + 1 \right)} \)

Problem 2.1925 · hard

Differentiate \( \displaystyle f(x) = 2 x \ln{\left(4 x + 2 \right)} - 2 x + \ln{\left(2 x + 1 \right)} \).
  1. \[ \frac{d}{d x} \left(2 x \ln{\left(4 x + 2 \right)} - 2 x + \ln{\left(2 x + 1 \right)}\right) \]
    derivativeStart with the derivative of the function.✓ Proved
  2. \[ = - \frac{d}{d x} 2 x + \frac{d}{d x} 2 x \ln{\left(4 x + 2 \right)} + \frac{d}{d x} \ln{\left(2 x + 1 \right)} \]
    sumApply the sum rule for derivatives.✓ Proved
  3. \[ = \frac{d}{d x} 2 x \ln{\left(4 x + 2 \right)} + \frac{d}{d x} \ln{\left(2 x + 1 \right)} - 2 \]
    constantDifferentiate the linear term -2*x.✓ Proved
  4. \[ = 2 x \frac{d}{d x} \ln{\left(4 x + 2 \right)} + \ln{\left(4 x + 2 \right)} \frac{d}{d x} 2 x + \frac{d}{d x} \ln{\left(2 x + 1 \right)} - 2 \]
    productApply the product rule to the first term.✓ Proved
  5. \[ = 2 x \frac{d}{d x} \ln{\left(4 x + 2 \right)} + 2 \ln{\left(4 x + 2 \right)} + \frac{d}{d x} \ln{\left(2 x + 1 \right)} - 2 \]
    constant-multipleDifferentiate the term 2*x.✓ Proved
  6. \[ = \frac{2 x \frac{d}{d x} \left(4 x + 2\right)}{4 x + 2} + 2 \ln{\left(4 x + 2 \right)} + \frac{d}{d x} \ln{\left(2 x + 1 \right)} - 2 \]
    chainApply the chain rule to the logarithm.✓ Proved
  7. \[ = \frac{8 x}{4 x + 2} + 2 \ln{\left(4 x + 2 \right)} + \frac{d}{d x} \ln{\left(2 x + 1 \right)} - 2 \]
    derivativeDifferentiate the inner function 4*x + 2.✓ Proved
  8. \[ = \frac{8 x}{4 x + 2} + 2 \ln{\left(4 x + 2 \right)} - 2 + \frac{\frac{d}{d x} \left(2 x + 1\right)}{2 x + 1} \]
    chainApply the chain rule to the second logarithm.✓ Proved
  9. \[ = \frac{8 x}{4 x + 2} + 2 \ln{\left(4 x + 2 \right)} - 2 + \frac{2}{2 x + 1} \]
    derivative algebraDifferentiate the inner function 2*x + 1. Multiply the terms in the numerator.✓ Proved
  10. \[ = \frac{4 x}{2 x + 1} + 2 \ln{\left(4 x + 2 \right)} - 2 + \frac{2}{2 x + 1} \]
    algebraSimplify the fraction (8*x)/(4*x + 2) by dividing by 2.✓ Proved
  11. \[ = 2 \ln{\left(4 x + 2 \right)} - 2 + \frac{4 x + 2}{2 x + 1} \]
    algebra algebraCombine the fractions with the same denominator. Factor the numerator 4*x + 2.✓ Proved
  12. \[ = 2 \ln{\left(4 x + 2 \right)} \]
    algebra simplifyCancel the common factor (2*x + 1). Final simplification.✓ Proved
Answer \( 2 \ln{\left(4 x + 2 \right)} \)

✓ 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 4*x + 2 = 0
7✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
log is undefined for non-positive arguments
undefined where 4*x + 2 = 0
8✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
log is undefined for non-positive arguments
undefined where 4*x + 2 = 0
undefined where 2*x + 1 = 0
9✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
log is undefined for non-positive arguments
undefined where 2*x + 1 = 0
undefined where 4*x + 2 = 0
10✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
log is undefined for non-positive arguments
undefined where 2*x + 1 = 0
undefined where 4*x + 2 = 0
11✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
log is undefined for non-positive arguments
undefined where 2*x + 1 = 0
undefined where 4*x + 2 = 0
12✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
log is undefined for non-positive arguments
undefined where 2*x + 1 = 0
13✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
log is undefined for non-positive arguments
undefined where 2*x + 1 = 0
14✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
log is undefined for non-positive arguments
undefined where 2*x + 1 = 0
15✓ 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 step-by-step, adhering to the one-change-per-step constraint. All labels are appropriate for the transformations performed.
Every verdict on record (4)
  • gpt-oss:20b: 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. All labels are appropriate for the transformations performed.
  • gpt-oss:20b: 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. The algebraic simplifications are valid and clearly labeled.

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.