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Derivative of \( \displaystyle \frac{3 \sqrt{\left(5 x + 2\right)^{2} + 1}}{5} \)

Problem 2.1346 · medium

Differentiate \( \displaystyle f(x) = \frac{3 \sqrt{\left(5 x + 2\right)^{2} + 1}}{5} \).
  1. \[ \frac{d}{d x} \frac{3 \sqrt{\left(5 x + 2\right)^{2} + 1}}{5} \]
    derivativeStart with the derivative of the function.✓ Proved
  2. \[ = \frac{3 \frac{d}{d x} \sqrt{\left(5 x + 2\right)^{2} + 1}}{5} \]
    constant-multiple rewritePull out the constant factor. Rewrite the square root as a fractional exponent.✓ Proved
  3. \[ = \frac{3 \frac{d}{d x} \left(\left(5 x + 2\right)^{2} + 1\right)}{10 \sqrt{\left(5 x + 2\right)^{2} + 1}} \]
    chain algebraApply the chain rule. Simplify the constant coefficient.✓ Proved
  4. \[ = \frac{3 \frac{d}{d x} \left(5 x + 2\right)^{2}}{10 \sqrt{\left(5 x + 2\right)^{2} + 1}} \]
    sumDifferentiate the sum term by term.✓ Proved
  5. \[ = \frac{3 \left(10 x + 4\right) \frac{d}{d x} \left(5 x + 2\right)}{10 \sqrt{\left(5 x + 2\right)^{2} + 1}} \]
    powerApply the power rule to the squared term.✓ Proved
  6. \[ = \frac{3 \left(50 x + 20\right)}{10 \sqrt{\left(5 x + 2\right)^{2} + 1}} \]
    derivative algebraDifferentiate the linear term. Multiply the constants.✓ Proved
  7. \[ = \frac{15 x + 6}{\sqrt{\left(5 x + 2\right)^{2} + 1}} \]
    algebraSimplify the expression by canceling 10/10.✓ Proved
  8. \[ = \frac{15 x + 6}{\sqrt{25 x^{2} + 20 x + 5}} \]
    simplifyExpand and simplify the denominator.✓ Proved
Answer \( \frac{3 \left(5 x + 2\right)}{\sqrt{\left(5 x + 2\right)^{2} + 1}} \)

✓ 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
3✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
4✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where (5*x + 2)**2 + 1 = 0
5✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where (5*x + 2)**2 + 1 = 0
6✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where (5*x + 2)**2 + 1 = 0
7✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where (5*x + 2)**2 + 1 = 0
8✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where (5*x + 2)**2 + 1 = 0
9✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where (5*x + 2)**2 + 1 = 0
10✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where (5*x + 2)**2 + 1 = 0
11✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where (5*x + 2)**2 + 1 = 0
undefined where 25*x**2 + 20*x + 5 = 0
answer✓ Provedsympy 1.14.0final line against the stated answer: simplify(a - b) reduced to 0
undefined where (5*x + 2)**2 + 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: fail (style) — Step 6 is labeled 'sum' but performs no differentiation; it simply drops the derivative of the constant term 1, which is an algebraic simplification or rewrite, not the application of the sum rule for differentiation. Additionally, Step 7 is labeled 'power' but applies the chain rule to the squared term (u^2 -> 2u*u'), which is a defect in labeling.
Every verdict on record (4)
  • qwen3.6:27b-mlx: fail (style) 2026-10-03 — Step 6 is labeled 'sum' but performs no differentiation; it simply drops the derivative of the constant term 1, which is an algebraic simplification or rewrite, not the application of the sum rule for differentiation. Additionally, Step 7 is labeled 'power' but applies the chain rule to the squared term (u^2 -> 2u*u'), which is a defect in labeling.
  • gpt-oss:20b: pass 2026-10-03
  • qwen3.6:27b-mlx: pass 2026-09-30 — The solution correctly applies differentiation rules step-by-step, adhering to the one-change-per-step constraint. The labels accurately describe the operations performed, and the final simplification is valid.
  • gpt-oss:20b: pass 2026-09-30

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 2026-10-03 with SymPy 1.14.0.