Derivative of \( \displaystyle \frac{3 \sqrt{\left(5 x + 2\right)^{2} + 1}}{5} \)
Problem 2.1346 · medium
Differentiate \( \displaystyle f(x) = \frac{3 \sqrt{\left(5 x + 2\right)^{2} + 1}}{5} \).
- \[ \frac{d}{d x} \frac{3 \sqrt{\left(5 x + 2\right)^{2} + 1}}{5} \]derivativeStart with the derivative of the function.✓ Proved
- \[ = \frac{3 \frac{d}{d x} \sqrt{\left(5 x + 2\right)^{2} + 1}}{5} \]constant-multiple rewritePull out the constant factor. Rewrite the square root as a fractional exponent.✓ Proved
- \[ = \frac{3 \frac{d}{d x} \left(\left(5 x + 2\right)^{2} + 1\right)}{10 \sqrt{\left(5 x + 2\right)^{2} + 1}} \]chain algebraApply the chain rule. Simplify the constant coefficient.✓ Proved
- \[ = \frac{3 \frac{d}{d x} \left(5 x + 2\right)^{2}}{10 \sqrt{\left(5 x + 2\right)^{2} + 1}} \]sumDifferentiate the sum term by term.✓ Proved
- \[ = \frac{3 \left(10 x + 4\right) \frac{d}{d x} \left(5 x + 2\right)}{10 \sqrt{\left(5 x + 2\right)^{2} + 1}} \]powerApply the power rule to the squared term.✓ Proved
- \[ = \frac{3 \left(50 x + 20\right)}{10 \sqrt{\left(5 x + 2\right)^{2} + 1}} \]derivative algebraDifferentiate the linear term. Multiply the constants.✓ Proved
- \[ = \frac{15 x + 6}{\sqrt{\left(5 x + 2\right)^{2} + 1}} \]algebraSimplify the expression by canceling 10/10.✓ Proved
- \[ = \frac{15 x + 6}{\sqrt{25 x^{2} + 20 x + 5}} \]simplifyExpand and simplify the denominator.✓ Proved
Answer \( \frac{3 \left(5 x + 2\right)}{\sqrt{\left(5 x + 2\right)^{2} + 1}} \)
✓ 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 (5*x + 2)**2 + 1 = 0 |
| 5 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where (5*x + 2)**2 + 1 = 0 |
| 6 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where (5*x + 2)**2 + 1 = 0 |
| 7 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where (5*x + 2)**2 + 1 = 0 |
| 8 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where (5*x + 2)**2 + 1 = 0 |
| 9 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where (5*x + 2)**2 + 1 = 0 |
| 10 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where (5*x + 2)**2 + 1 = 0 |
| 11 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where (5*x + 2)**2 + 1 = 0 undefined where 25*x**2 + 20*x + 5 = 0 |
| answer | ✓ Proved | sympy 1.14.0 | final line against the stated answer: simplify(a - b) reduced to 0 undefined where (5*x + 2)**2 + 1 = 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: fail (style) — Step 6 is labeled 'sum' but performs no differentiation; it simply drops the derivative of the constant term 1, which is an algebraic simplification or rewrite, not the application of the sum rule for differentiation. Additionally, Step 7 is labeled 'power' but applies the chain rule to the squared term (u^2 -> 2u*u'), which is a defect in labeling.
Every verdict on record (4)
qwen3.6:27b-mlx: fail (style) 2026-10-03 — Step 6 is labeled 'sum' but performs no differentiation; it simply drops the derivative of the constant term 1, which is an algebraic simplification or rewrite, not the application of the sum rule for differentiation. Additionally, Step 7 is labeled 'power' but applies the chain rule to the squared term (u^2 -> 2u*u'), which is a defect in labeling.gpt-oss:20b: pass 2026-10-03qwen3.6:27b-mlx: pass 2026-09-30 — The solution correctly applies differentiation rules step-by-step, adhering to the one-change-per-step constraint. The labels accurately describe the operations performed, and the final simplification is valid.gpt-oss:20b: pass 2026-09-30
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 2026-10-03 with SymPy 1.14.0.