Derivative of \( \displaystyle \frac{5 \sqrt{4 x^{2} + 4 x + 2}}{2} \)
Problem 2.1495 · hard
Differentiate \( \displaystyle f(x) = \frac{5 \sqrt{4 x^{2} + 4 x + 2}}{2} \).
- \[ \frac{d}{d x} \frac{5 \sqrt{4 x^{2} + 4 x + 2}}{2} \]Start with the derivative of the function.✓ Proved
- \[ = \frac{5 \frac{d}{d x} \sqrt{4 x^{2} + 4 x + 2}}{2} \]constant-multiple rewritePull out the constant factor. Rewrite the square root as a fractional power.✓ Proved
- \[ = \frac{5 \frac{d}{d x} \left(4 x^{2} + 4 x + 2\right)}{4 \sqrt{4 x^{2} + 4 x + 2}} \]chain algebraApply the chain rule. Distribute the power term.✓ Proved
- \[ = \frac{5 \left(\frac{d}{d x} 2 + \frac{d}{d x} 4 x + \frac{d}{d x} 4 x^{2}\right)}{4 \sqrt{4 x^{2} + 4 x + 2}} \]sumDifferentiate the sum term by term.✓ Proved
- \[ = \frac{5 \left(8 x + 4\right)}{4 \sqrt{4 x^{2} + 4 x + 2}} \]derivative constantCompute the derivatives of the individual terms. The derivative of the constant 2 is 0.✓ Proved
- \[ = \frac{10 x + 5}{\sqrt{4 x^{2} + 4 x + 2}} \]rewrite algebraRewrite the negative exponent as a denominator. Factor out 4 from (8x + 4) and simplify with 5/4.✓ Proved
Answer \( \frac{10 x + 5}{\sqrt{4 x^{2} + 4 x + 2}} \)
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. The reviewers disagree about how one step is explained; every verdict is in the receipt.
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 4*x**2 + 4*x + 2 = 0 |
| 5 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where 4*x**2 + 4*x + 2 = 0 |
| 6 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where 4*x**2 + 4*x + 2 = 0 |
| 7 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where 4*x**2 + 4*x + 2 = 0 |
| 8 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where 4*x**2 + 4*x + 2 = 0 |
| 9 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where 4*x**2 + 4*x + 2 = 0 |
| 10 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where 4*x**2 + 4*x + 2 = 0 |
| answer | ✓ Proved | sympy 1.14.0 | final line against the stated answer: simplify(a - b) reduced to 0 undefined where 4*x**2 + 4*x + 2 = 0 |
| answer, a second way | ✓ Proved | sympy 1.14.0 | SymPy differentiated f directly and got the stated answer |
Reviewers
gpt-oss:20b: fail (error) — Step 1 lacks a proper label – it should be "derivative". Step 5’s note claims to distribute the power term, but no such distribution occurs; only the constants are multiplied. Step 8 incorrectly labels the derivative of the constant 2 as "constant" – it should be "derivative".qwen3.6:27b-mlx: fail (style) — Step 5 is a no-op that does not apply the 'algebra' rule to change the expression (it merely restates 4*x**2 as 4*x*x without effecting a simplification or transformation), and Step 8 is labeled 'constant' but performs algebraic simplification (removing +0) rather than applying a differentiation rule.
Every verdict on record (4)
qwen3.6:27b-mlx: fail (style) 2026-10-04 — Step 5 is a no-op that does not apply the 'algebra' rule to change the expression (it merely restates 4*x**2 as 4*x*x without effecting a simplification or transformation), and Step 8 is labeled 'constant' but performs algebraic simplification (removing +0) rather than applying a differentiation rule.gpt-oss:20b: fail (error) 2026-10-04 — Step 1 lacks a proper label – it should be "derivative". Step 5’s note claims to distribute the power term, but no such distribution occurs; only the constants are multiplied. Step 8 incorrectly labels the derivative of the constant 2 as "constant" – it should be "derivative".qwen3.6:27b-mlx: pass 2026-10-04gpt-oss:20b: pass 2026-10-04
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 2026-10-04 with SymPy 1.14.0.