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Derivative of \( \displaystyle \frac{2 \sqrt{9 x^{2} + 6 x + 2}}{3} \)

Problem 2.1776 · hard

Differentiate \( \displaystyle f(x) = \frac{2 \sqrt{9 x^{2} + 6 x + 2}}{3} \).
  1. \[ \frac{d}{d x} \frac{2 \sqrt{9 x^{2} + 6 x + 2}}{3} \]
    derivativeStart with the derivative of the function.✓ Proved
  2. \[ = \frac{2 \frac{d}{d x} \sqrt{9 x^{2} + 6 x + 2}}{3} \]
    constant-multiple rewritePull out the constant factor. Rewrite the square root as a fractional power.✓ Proved
  3. \[ = \frac{\frac{d}{d x} \left(9 x^{2} + 6 x + 2\right)}{3 \sqrt{9 x^{2} + 6 x + 2}} \]
    chain algebraApply the chain rule. Simplify the constant coefficients.✓ Proved
  4. \[ = \frac{18 x + 6}{3 \sqrt{9 x^{2} + 6 x + 2}} \]
    derivativeDifferentiate the polynomial inside.✓ Proved
  5. \[ = \frac{2 \left(3 x + 1\right)}{\sqrt{9 x^{2} + 6 x + 2}} \]
    algebraFactor out 6 from the derivative.✓ Proved
  6. \[ = \frac{6 x + 2}{\sqrt{9 x^{2} + 6 x + 2}} \]
    algebra algebra rewrite simplifySimplify the product of constants. Move the power to the denominator. Rewrite the fractional power as a square root. Factor out 2 from the numerator.✓ Proved
Answer \( \frac{2 \left(3 x + 1\right)}{\sqrt{9 x^{2} + 6 x + 2}} \)

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. The reviewers disagree about how one step is explained; every verdict is in the receipt.

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

Reviewers

  • gpt-oss:20b: fail (error) — Step 4 applies both the power rule and the chain rule in a single step, violating the rule that each step must change only one thing.
  • qwen3.6:27b-mlx: pass
Every verdict on record (4)
  • gpt-oss:20b: fail (error) 2026-10-07 — Step 4 applies both the power rule and the chain rule in a single step, violating the rule that each step must change only one thing.
  • qwen3.6:27b-mlx: pass 2026-10-07
  • gpt-oss:20b: pass 2026-10-07
  • qwen3.6:27b-mlx: pass 2026-10-07

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 2026-10-07 with SymPy 1.14.0.