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

Problem 2.1522 · hard

Differentiate \( \displaystyle f(x) = \sqrt{9 x^{2} + 6 x + 2} \).
  1. \[ \frac{d}{d x} \sqrt{9 x^{2} + 6 x + 2} \]
    derivative rewriteStart with the derivative of the function. Rewrite the square root as a fractional exponent.✓ Proved
  2. \[ = \frac{\frac{d}{d x} \left(9 x^{2} + 6 x + 2\right)}{2 \sqrt{9 x^{2} + 6 x + 2}} \]
    chainApply the chain rule.✓ Proved
  3. \[ = \frac{\frac{d}{d x} 2 + \frac{d}{d x} 6 x + \frac{d}{d x} 9 x^{2}}{2 \sqrt{9 x^{2} + 6 x + 2}} \]
    sumDifferentiate the sum inside the parentheses.✓ Proved
  4. \[ = \frac{18 x + 6}{2 \sqrt{9 x^{2} + 6 x + 2}} \]
    derivative constantDifferentiate each term individually. The derivative of the constant 2 is 0.✓ Proved
  5. \[ = \frac{9 x + 3}{\sqrt{9 x^{2} + 6 x + 2}} \]
    constant-multiple simplifyDistribute the 1/2 into the parentheses. Rewrite the negative exponent as a fraction.✓ Proved
Answer \( \frac{9 x + 3}{\sqrt{9 x^{2} + 6 x + 2}} \)

✓ 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
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
undefined where 9*x**2 + 6*x + 2 = 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
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: pass
Every verdict on record (4)
  • qwen3.6:27b-mlx: pass 2026-10-04
  • gpt-oss:20b: pass 2026-10-04
  • qwen3.6:27b-mlx: pass 2026-10-04
  • gpt-oss:20b: pass 2026-10-04

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 2026-10-04 with SymPy 1.14.0.