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Derivative of \( \displaystyle \frac{\sqrt{4 x + 1}}{4 x + 2} \)

Problem 2.441 · hard

Differentiate \( \displaystyle f(x) = \frac{\sqrt{4 x + 1}}{4 x + 2} \).
  1. \[ \frac{d}{d x} \frac{\sqrt{4 x + 1}}{4 x + 2} \]
    rewriteStart with the derivative of the function. Rewrite the denominator using a negative exponent.✓ Proved
  2. \[ = \sqrt{4 x + 1} \frac{d}{d x} \frac{1}{4 x + 2} + \frac{\frac{d}{d x} \sqrt{4 x + 1}}{4 x + 2} \]
    product rewriteApply the product rule. Rewrite the square root as a fractional power.✓ Proved
  3. \[ = \sqrt{4 x + 1} \frac{d}{d x} \frac{1}{4 x + 2} + \frac{2}{\sqrt{4 x + 1} \left(4 x + 2\right)} \]
    chainApply the chain rule to the first term.✓ Proved
  4. \[ = - \frac{4 \sqrt{4 x + 1}}{\left(4 x + 2\right)^{2}} + \frac{2}{\sqrt{4 x + 1} \left(4 x + 2\right)} \]
    chain constant-multiple algebraApply the chain rule to the second term. Simplify the constants. Distribute the exponents.✓ Proved
  5. \[ = - \frac{8 x}{\sqrt{4 x + 1} \left(4 x + 2\right)^{2}} \]
    algebra algebra algebra simplifyFind a common denominator. Simplify the numerator. Distribute the 4. Combine like terms.✓ Proved
Answer \( - \frac{2 x}{\left(2 x + 1\right)^{2} \sqrt{4 x + 1}} \)

✓ 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 4*x + 2 = 0
3✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where 4*x + 2 = 0
4✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where 4*x + 2 = 0
5✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where 4*x + 2 = 0
undefined where 4*x + 1 = 0
6✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where 4*x + 2 = 0
undefined where 4*x + 1 = 0
7✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where 4*x + 2 = 0
undefined where 4*x + 1 = 0
8✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where 4*x + 2 = 0
undefined where 4*x + 1 = 0
9✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where 4*x + 2 = 0
undefined where 4*x + 1 = 0
10✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where 4*x + 2 = 0
undefined where 4*x + 1 = 0
11✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where 4*x + 2 = 0
undefined where 4*x + 1 = 0
12✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where 4*x + 2 = 0
undefined where 4*x + 1 = 0
answer✓ Provedsympy 1.14.0final line against the stated answer: simplify(a - b) reduced to 0
undefined where 2*x + 1 = 0
undefined where 4*x + 1 = 0
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 (6)
  • qwen3.6:27b-mlx: pass 2026-09-21
  • gpt-oss:20b: pass 2026-09-21
  • qwen3.6:27b-mlx: pass 2026-09-20
  • gpt-oss:20b: pass 2026-09-20
  • qwen3.6:27b-mlx: pass 2026-09-20
  • gpt-oss:20b: pass 2026-09-20

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.