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Derivative of \( \displaystyle 5 \sqrt{\left(x - 1\right)^{2} + 1} \)

Problem 2.995 · medium

Differentiate \( \displaystyle f(x) = 5 \sqrt{\left(x - 1\right)^{2} + 1} \).
  1. \[ \frac{d}{d x} 5 \sqrt{\left(x - 1\right)^{2} + 1} \]
    derivativeStart with the derivative of the function.✓ Proved
  2. \[ = 5 \frac{d}{d x} \sqrt{\left(x - 1\right)^{2} + 1} \]
    constant-multiple rewritePull out the constant factor 5. Rewrite the square root as a power.✓ Proved
  3. \[ = \frac{5 \frac{d}{d x} \left(\left(x - 1\right)^{2} + 1\right)}{2 \sqrt{\left(x - 1\right)^{2} + 1}} \]
    chainApply the chain rule.✓ Proved
  4. \[ = \frac{5 \frac{d}{d x} \left(x^{2} - 2 x + 2\right)}{2 \sqrt{\left(x - 1\right)^{2} + 1}} \]
    algebraExpand the inner quadratic expression.✓ Proved
  5. \[ = \frac{5 \left(2 x - 2\right)}{2 \sqrt{\left(x - 1\right)^{2} + 1}} \]
    derivative algebraDifferentiate the inner polynomial. Factor out the 2 from the derivative.✓ Proved
  6. \[ = \frac{5 x - 5}{\sqrt{\left(x - 1\right)^{2} + 1}} \]
    algebra simplifyMultiply the constants (5 * 1/2 * 2). Rewrite the negative exponent as a denominator.✓ Proved
Answer \( \frac{5 \left(x - 1\right)}{\sqrt{\left(x - 1\right)^{2} + 1}} \)

✓ 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
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
undefined where (x - 1)**2 + 1 = 0
5✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where (x - 1)**2 + 1 = 0
6✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where (x - 1)**2 + 1 = 0
7✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where (x - 1)**2 + 1 = 0
8✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where (x - 1)**2 + 1 = 0
9✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where (x - 1)**2 + 1 = 0
answer✓ Provedsympy 1.14.0final line against the stated answer: simplify(a - b) reduced to 0
undefined where (x - 1)**2 + 1 = 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: pass
Every verdict on record (4)
  • qwen3.6:27b-mlx: pass 2026-09-27
  • gpt-oss:20b: pass 2026-09-27
  • qwen3.6:27b-mlx: pass 2026-09-27
  • gpt-oss:20b: pass 2026-09-27

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 2026-09-27 with SymPy 1.14.0.