Derivative of \( \displaystyle 3 \sqrt{x^{2} + 4 x + 5} \)
Problem 2.1854 · hard
Differentiate \( \displaystyle f(x) = 3 \sqrt{x^{2} + 4 x + 5} \).
- \[ \frac{d}{d x} 3 \sqrt{x^{2} + 4 x + 5} \]derivativeStart with the derivative of the function.✓ Proved
- \[ = 3 \frac{d}{d x} \sqrt{x^{2} + 4 x + 5} \]constant-multiple rewritePull the constant out of the derivative. Rewrite the square root as a fractional power.✓ Proved
- \[ = \frac{3 \frac{d}{d x} \left(x^{2} + 4 x + 5\right)}{2 \sqrt{x^{2} + 4 x + 5}} \]chainApply the chain rule.✓ Proved
- \[ = \frac{3 \left(2 x + 4\right)}{2 \sqrt{x^{2} + 4 x + 5}} \]derivativeDifferentiate the inner function.✓ Proved
- \[ = \frac{3 \left(x + 2\right)}{\sqrt{x^{2} + 4 x + 5}} \]algebraFactor out a 2 from the inner derivative.✓ Proved
- \[ = \frac{3 x + 6}{\sqrt{x^{2} + 4 x + 5}} \]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
| Line | Status | Checked by | Detail |
|---|---|---|---|
| 1 | ✓ Proved | sympy 1.14.0 | line 1 is the problem as stated |
| 2 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 |
| 3 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 |
| 4 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where x**2 + 4*x + 5 = 0 |
| 5 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where x**2 + 4*x + 5 = 0 |
| 6 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where x**2 + 4*x + 5 = 0 |
| 7 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where x**2 + 4*x + 5 = 0 |
| 8 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where x**2 + 4*x + 5 = 0 |
| answer | ✓ Proved | sympy 1.14.0 | final line against the stated answer: simplify(a - b) reduced to 0 undefined where x**2 + 4*x + 5 = 0 |
| answer, a second way | ✓ Proved | sympy 1.14.0 | SymPy differentiated f directly and got the stated answer |
Reviewers
gpt-oss:20b: passqwen3.6:27b-mlx: pass
Every verdict on record (4)
gpt-oss:20b: pass 2026-10-08qwen3.6:27b-mlx: pass 2026-10-08gpt-oss:20b: pass 2026-10-08qwen3.6:27b-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.