Derivative of \( \displaystyle 5 x \left(x - 6\right) \)
Problem 2.667 · medium
Differentiate \( \displaystyle f(x) = 5 x \left(x - 6\right) \).
- \[ \frac{d}{d x} 5 x \left(x - 6\right) \]derivativeStart with the derivative of the function.✓ Proved
- \[ = 5 \frac{d}{d x} x \left(x - 6\right) \]constant-multiplePull out the constant factor 5.✓ Proved
- \[ = 5 x \frac{d}{d x} \left(x - 6\right) + 5 \left(x - 6\right) \frac{d}{d x} x \]productApply the product rule.✓ Proved
- \[ = 5 x \frac{d}{d x} \left(x - 6\right) + 5 x - 30 \]derivativeDifferentiate the first part of the product.✓ Proved
- \[ = 5 x \left(- \frac{d}{d x} 6 + \frac{d}{d x} x\right) + 5 x - 30 \]sumDifferentiate the second part of the product.✓ Proved
- \[ = 10 x - 30 \]derivative algebra algebra simplifyDifferentiate the terms inside the parentheses. Simplify the expression inside the parentheses. Combine like terms. Distribute the 5 to get the final answer.✓ Proved
Answer \( 10 x - 30 \)
✓ 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 |
| 5 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 |
| 6 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 |
| 7 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 |
| 8 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 |
| 9 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 |
| answer | ✓ Proved | sympy 1.14.0 | final line against the stated answer: simplify(a - b) reduced to 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)
qwen3.6:27b-mlx: pass 2026-09-21gpt-oss:20b: pass 2026-09-21qwen3.6:27b-mlx: pass 2026-09-21gpt-oss:20b: pass 2026-09-21
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 2026-09-26 with SymPy 1.14.0.