∫Calc Practice
Home›Calculus 1›Chain rule›Problem 2.1912

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

Problem 2.1912 · hard

Differentiate \( \displaystyle f(x) = - \frac{\sqrt{9 x^{2} - 6 x + 2}}{3} \).
  1. \[ \frac{d}{d x} \left(- \frac{\sqrt{9 x^{2} - 6 x + 2}}{3}\right) \]
    constant-multipleStart with the derivative of the function.✓ Proved
  2. \[ = - \frac{\frac{d}{d x} \sqrt{9 x^{2} - 6 x + 2}}{3} \]
    constant-multiple rewritePull out the constant factor. Rewrite the square root as a power.✓ Proved
  3. \[ = - \frac{\frac{d}{d x} \left(9 x^{2} - 6 x + 2\right)}{6 \sqrt{9 x^{2} - 6 x + 2}} \]
    chain algebraApply the chain rule. Simplify the constant coefficient.✓ Proved
  4. \[ = - \frac{\frac{d}{d x} 2 - \frac{d}{d x} 6 x + \frac{d}{d x} 9 x^{2}}{6 \sqrt{9 x^{2} - 6 x + 2}} \]
    sumDifferentiate the terms inside the parentheses separately.✓ Proved
  5. \[ = - \frac{18 x - 6}{6 \sqrt{9 x^{2} - 6 x + 2}} \]
    derivative constantCalculate the derivatives of each term. The derivative of the constant 2 is 0.✓ Proved
  6. \[ = \frac{1 - 3 x}{\sqrt{9 x^{2} - 6 x + 2}} \]
    algebraRearrange the terms.✓ Proved
  7. \[ = \frac{6 - 18 x}{6 \sqrt{9 x^{2} - 6 x + 2}} \]
    algebraMove the negative exponent to the denominator.✓ Proved
  8. \[ = \frac{1 - 3 x}{\sqrt{9 x^{2} - 6 x + 2}} \]
    simplifySimplify the fraction by dividing by 6.✓ Proved
Answer \( \frac{1 - 3 x}{\sqrt{9 x^{2} - 6 x + 2}} \)

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: pass
  • qwen3.6:27b-mlx: fail (error) — Step 6 applies the sum rule to split the derivative, but it also changes the term 9*x**2 to 9*x*x, which is an algebraic rewrite not covered by the 'sum' rule. This violates the one-rule-per-step constraint.
Every verdict on record (4)
  • gpt-oss:20b: pass 2026-10-09
  • qwen3.6:27b-mlx: fail (error) 2026-10-09 — Step 6 applies the sum rule to split the derivative, but it also changes the term 9*x**2 to 9*x*x, which is an algebraic rewrite not covered by the 'sum' rule. This violates the one-rule-per-step constraint.
  • gpt-oss:20b: pass 2026-10-09
  • qwen3.6:27b-mlx: fail (error) 2026-10-09 — Step 1 is labeled 'constant-multiple' but performs no operation; it merely restates the problem, violating the rule that each step must change one thing. Step 8 is labeled 'constant' but performs algebraic simplification (removing +0), not a differentiation rule.

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 2026-10-09 with SymPy 1.14.0.