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

Problem 2.2011 · medium

Differentiate \( \displaystyle f(x) = 3 x^{2} + 2 x \).
  1. \[ \frac{d}{d x} \left(3 x^{2} + 2 x\right) \]
    sumStart with the derivative of the entire function.✓ Proved
  2. \[ = \frac{d}{d x} 2 x + \frac{d}{d x} 3 x^{2} \]
    sumApply the sum rule to differentiate each term separately.✓ Proved
  3. \[ = \frac{d}{d x} 2 x + 3 \frac{d}{d x} x^{2} \]
    constant-multiplePull the constant 3 out of the first derivative.✓ Proved
  4. \[ = 2 \frac{d}{d x} x + 3 \frac{d}{d x} x^{2} \]
    constant-multiplePull the constant 2 out of the second derivative.✓ Proved
  5. \[ = 6 x + 2 \]
    power algebraApply the power rule to both terms. Multiply the constants through the parentheses.✓ Proved
Answer \( 6 x + 2 \)

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
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
5✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
6✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
answer✓ Provedsympy 1.14.0final line against the stated answer: simplify(a - b) reduced to 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: fail (error) — Step 5 applies the power rule to both terms simultaneously, violating the constraint that each step must change only one thing. It should be split into two steps.
Every verdict on record (4)
  • gpt-oss:20b: pass 2026-10-10
  • qwen3.6:27b-mlx: fail (error) 2026-10-10 — Step 5 applies the power rule to both terms simultaneously, violating the constraint that each step must change only one thing. It should be split into two steps.
  • gpt-oss:20b: pass 2026-10-10
  • qwen3.6:27b-mlx: fail (error) 2026-10-10 — Step 5 applies the power rule to both terms simultaneously, violating the one-change-per-step constraint. It should be split into two steps.

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 2026-10-10 with SymPy 1.14.0.