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

Problem 2.1738 · hard

Differentiate \( \displaystyle f(x) = 2 \sqrt{x^{2} + 2 x + 2} \).
  1. \[ \frac{d}{d x} 2 \sqrt{x^{2} + 2 x + 2} \]
    derivativeStart with the derivative of the function.✓ Proved
  2. \[ = 2 \frac{d}{d x} \sqrt{x^{2} + 2 x + 2} \]
    constant-multiple rewritePull out the constant factor 2. Rewrite the square root as a power.✓ Proved
  3. \[ = \frac{\frac{d}{d x} \left(x^{2} + 2 x + 2\right)}{\sqrt{x^{2} + 2 x + 2}} \]
    chain algebraApply the chain rule. Simplify the constant factors.✓ Proved
  4. \[ = \frac{2 x + 2}{\sqrt{x^{2} + 2 x + 2}} \]
    derivative algebra simplifyDifferentiate the inner polynomial. Rewrite with a positive exponent. Factor out the 2 in the numerator.✓ Proved
Answer \( \frac{2 \left(x + 1\right)}{\sqrt{x^{2} + 2 x + 2}} \)

✓ 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
4✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where x**2 + 2*x + 2 = 0
5✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where x**2 + 2*x + 2 = 0
6✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where x**2 + 2*x + 2 = 0
7✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where x**2 + 2*x + 2 = 0
8✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where x**2 + 2*x + 2 = 0
answer✓ Provedsympy 1.14.0final line against the stated answer: simplify(a - b) reduced to 0
undefined where x**2 + 2*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 2026-10-07
  • gpt-oss:20b: pass 2026-10-07
  • qwen3.6:27b-mlx: pass 2026-10-07
  • gpt-oss:20b: 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.