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Derivative of \( \displaystyle 3 \sqrt{x^{2} + 4 x + 5} \)

Problem 2.1854 · hard

Differentiate \( \displaystyle f(x) = 3 \sqrt{x^{2} + 4 x + 5} \).
  1. \[ \frac{d}{d x} 3 \sqrt{x^{2} + 4 x + 5} \]
    derivativeStart with the derivative of the function.✓ Proved
  2. \[ = 3 \frac{d}{d x} \sqrt{x^{2} + 4 x + 5} \]
    constant-multiple rewritePull the constant out of the derivative. Rewrite the square root as a fractional power.✓ Proved
  3. \[ = \frac{3 \frac{d}{d x} \left(x^{2} + 4 x + 5\right)}{2 \sqrt{x^{2} + 4 x + 5}} \]
    chainApply the chain rule.✓ Proved
  4. \[ = \frac{3 \left(2 x + 4\right)}{2 \sqrt{x^{2} + 4 x + 5}} \]
    derivativeDifferentiate the inner function.✓ Proved
  5. \[ = \frac{3 \left(x + 2\right)}{\sqrt{x^{2} + 4 x + 5}} \]
    algebraFactor out a 2 from the inner derivative.✓ Proved
  6. \[ = \frac{3 x + 6}{\sqrt{x^{2} + 4 x + 5}} \]
    simplify simplifySimplify the coefficients. Rewrite with a positive exponent in the denominator.✓ Proved
Answer \( \frac{3 \left(x + 2\right)}{\sqrt{x^{2} + 4 x + 5}} \)

✓ 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 + 4*x + 5 = 0
5✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where x**2 + 4*x + 5 = 0
6✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where x**2 + 4*x + 5 = 0
7✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where x**2 + 4*x + 5 = 0
8✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where x**2 + 4*x + 5 = 0
answer✓ Provedsympy 1.14.0final line against the stated answer: simplify(a - b) reduced to 0
undefined where x**2 + 4*x + 5 = 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)
  • gpt-oss:20b: pass 2026-10-08
  • qwen3.6:27b-mlx: pass 2026-10-08
  • gpt-oss:20b: pass 2026-10-08
  • qwen3.6:27b-mlx: pass 2026-10-08

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 2026-10-08 with SymPy 1.14.0.