Derivative of \( \displaystyle \sqrt{4 x^{2} + 8 x + 5} \)
Problem 2.1658 · hard
Differentiate \( \displaystyle f(x) = \sqrt{4 x^{2} + 8 x + 5} \).
- \[ \frac{d}{d x} \sqrt{4 x^{2} + 8 x + 5} \]derivative rewriteStart with the derivative of the function. Rewrite the square root as a fractional exponent.✓ Proved
- \[ = \frac{\frac{d}{d x} \left(4 x^{2} + 8 x + 5\right)}{2 \sqrt{4 x^{2} + 8 x + 5}} \]chainApply the chain rule.✓ Proved
- \[ = \frac{\frac{d}{d x} 5 + \frac{d}{d x} 8 x + \frac{d}{d x} 4 x^{2}}{2 \sqrt{4 x^{2} + 8 x + 5}} \]sumDifferentiate the sum term by term.✓ Proved
- \[ = \frac{8 x + 8}{2 \sqrt{4 x^{2} + 8 x + 5}} \]derivative simplifyDifferentiate each term inside the parentheses. Simplify the expression.✓ Proved
- \[ = \frac{4 x + 4}{\sqrt{4 x^{2} + 8 x + 5}} \]algebra simplifyDistribute the 1/2 into the parentheses. Rewrite the negative exponent as a fraction.✓ Proved
Answer \( \frac{4 x + 4}{\sqrt{4 x^{2} + 8 x + 5}} \)
✓ 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 undefined where 4*x**2 + 8*x + 5 = 0 |
| 4 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where 4*x**2 + 8*x + 5 = 0 |
| 5 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where 4*x**2 + 8*x + 5 = 0 |
| 6 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where 4*x**2 + 8*x + 5 = 0 |
| 7 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where 4*x**2 + 8*x + 5 = 0 |
| 8 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where 4*x**2 + 8*x + 5 = 0 |
| answer | ✓ Proved | sympy 1.14.0 | final line against the stated answer: simplify(a - b) reduced to 0 undefined where 4*x**2 + 8*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 2026-10-06qwen3.6:27b-mlx: pass 2026-10-06qwen3.6:27b-mlx: pass 2026-10-06gpt-oss:20b: pass 2026-10-06
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 2026-10-06 with SymPy 1.14.0.