Derivative of \( \displaystyle \frac{4 x + 3}{2 x - 4} \)
Problem 2.315 · medium
Differentiate \( \displaystyle f(x) = \frac{4 x + 3}{2 x - 4} \).
- \[ \frac{d}{d x} \frac{4 x + 3}{2 x - 4} \]derivative rewriteStart with the derivative of the function. Rewrite the quotient as a product using a negative exponent.✓ Proved
- \[ = \left(4 x + 3\right) \frac{d}{d x} \frac{1}{2 x - 4} + \frac{\frac{d}{d x} \left(4 x + 3\right)}{2 x - 4} \]productApply the product rule.✓ Proved
- \[ = \left(4 x + 3\right) \frac{d}{d x} \frac{1}{2 x - 4} + \frac{4}{2 x - 4} \]derivativeDifferentiate the first term.✓ Proved
- \[ = \frac{\left(- 4 x - 3\right) \frac{d}{d x} \left(2 x - 4\right)}{\left(2 x - 4\right)^{2}} + \frac{4}{2 x - 4} \]chainApply the chain rule to the second term.✓ Proved
- \[ = \frac{2 \left(- 4 x - 3\right)}{\left(2 x - 4\right)^{2}} + \frac{4}{2 x - 4} \]derivativeDifferentiate the innermost function.✓ Proved
- \[ = \frac{4}{2 x - 4} - \frac{8 x + 6}{\left(2 x - 4\right)^{2}} \]algebraSimplify the negative exponents and coefficients.✓ Proved
- \[ = - \frac{22}{\left(2 x - 4\right)^{2}} \]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
| Line | Status | Checked by | Detail |
|---|---|---|---|
| 1 | ✓ Proved | sympy 1.14.0 | line 1 is the problem as stated |
| 2 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where 2*x - 4 = 0 |
| 3 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where 2*x - 4 = 0 |
| 4 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where 2*x - 4 = 0 |
| 5 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where 2*x - 4 = 0 |
| 6 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where 2*x - 4 = 0 |
| 7 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where 2*x - 4 = 0 |
| 8 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where 2*x - 4 = 0 |
| 9 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where 2*x - 4 = 0 |
| 10 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where 2*x - 4 = 0 |
| answer | ✓ Proved | sympy 1.14.0 | final line against the stated answer: simplify(a - b) reduced to 0 undefined where x - 2 = 0 |
| answer, a second way | ✓ Proved | sympy 1.14.0 | SymPy differentiated f directly and got the stated answer |
Reviewers
gpt-oss:20b: passdeepseek-r1:70b: passqwen3.6:27b-mlx: pass
Every verdict on record (12)
qwen3.6:27b-mlx: pass 2026-09-20gpt-oss:20b: pass 2026-09-20qwen3.6:27b-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 2026-09-20qwen3.6:27b-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 2026-09-19gpt-oss:20b: pass 2026-09-19qwen3.6:27b-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 2026-09-19gpt-oss:20b: pass 2026-09-19gpt-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.