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Derivative of \( \displaystyle \frac{4 x + 3}{2 x - 4} \)

Problem 2.315 · medium

Differentiate \( \displaystyle f(x) = \frac{4 x + 3}{2 x - 4} \).
  1. \[ \frac{d}{d x} \frac{4 x + 3}{2 x - 4} \]
    derivative rewriteStart with the derivative of the function. Rewrite the quotient as a product using a negative exponent.✓ Proved
  2. \[ = \left(4 x + 3\right) \frac{d}{d x} \frac{1}{2 x - 4} + \frac{\frac{d}{d x} \left(4 x + 3\right)}{2 x - 4} \]
    productApply the product rule.✓ Proved
  3. \[ = \left(4 x + 3\right) \frac{d}{d x} \frac{1}{2 x - 4} + \frac{4}{2 x - 4} \]
    derivativeDifferentiate the first term.✓ Proved
  4. \[ = \frac{\left(- 4 x - 3\right) \frac{d}{d x} \left(2 x - 4\right)}{\left(2 x - 4\right)^{2}} + \frac{4}{2 x - 4} \]
    chainApply the chain rule to the second term.✓ Proved
  5. \[ = \frac{2 \left(- 4 x - 3\right)}{\left(2 x - 4\right)^{2}} + \frac{4}{2 x - 4} \]
    derivativeDifferentiate the innermost function.✓ Proved
  6. \[ = \frac{4}{2 x - 4} - \frac{8 x + 6}{\left(2 x - 4\right)^{2}} \]
    algebraSimplify the negative exponents and coefficients.✓ Proved
  7. \[ = - \frac{22}{\left(2 x - 4\right)^{2}} \]
    algebra algebra simplifyCombine the terms over a common denominator. Distribute the terms in the numerator. Combine like terms to get the final result.✓ Proved
Answer \( - \frac{11}{2 \left(x - 2\right)^{2}} \)

✓ 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
undefined where 2*x - 4 = 0
3✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where 2*x - 4 = 0
4✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where 2*x - 4 = 0
5✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where 2*x - 4 = 0
6✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where 2*x - 4 = 0
7✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where 2*x - 4 = 0
8✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where 2*x - 4 = 0
9✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where 2*x - 4 = 0
10✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where 2*x - 4 = 0
answer✓ Provedsympy 1.14.0final line against the stated answer: simplify(a - b) reduced to 0
undefined where x - 2 = 0
answer, a second way✓ Provedsympy 1.14.0SymPy differentiated f directly and got the stated answer

Reviewers

  • gpt-oss:20b: pass
  • deepseek-r1:70b: pass
  • qwen3.6:27b-mlx: pass
Every verdict on record (12)
  • qwen3.6:27b-mlx: pass 2026-09-20
  • gpt-oss:20b: pass 2026-09-20
  • qwen3.6:27b-mlx: pass 2026-09-20 — The solution correctly applies the product rule, chain rule, and algebraic simplification steps. Each step changes only one aspect of the expression and uses valid labels from the vocabulary.
  • gpt-oss:20b: pass 2026-09-20
  • qwen3.6:27b-mlx: pass 2026-09-19 — The solution correctly applies the product rule, chain rule, and algebraic simplification. Each step isolates a single rule application, and the labels accurately reflect the operations performed.
  • deepseek-r1:70b: pass 2026-09-19
  • gpt-oss:20b: pass 2026-09-19
  • qwen3.6:27b-mlx: pass 2026-09-19 — The solution correctly applies the product rule, chain rule, and algebraic simplification. Each step modifies only one aspect of the expression and uses valid labels from the fixed vocabulary.
  • deepseek-r1:70b: pass 2026-09-19
  • gpt-oss:20b: pass 2026-09-19
  • gpt-oss:20b: fail 2026-09-17 — Step 10’s note says "Combine like terms to get the final result," yet the step only writes the intermediate expression –22/(2*x - 4)**2 and does not perform the final simplification to the stated answer –11/(2*(x - 2)**2). This misleads the reader into thinking the final answer is already reached.
  • deepseek-r1:70b: fail 2026-09-17 — The note in step 10 is misleading as it claims to present the final result without further simplification needed to 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 2026-09-26 with SymPy 1.14.0.