∫Calc Practice

Integral of \( \displaystyle 9 x^{2} e^{3 x} \)

Problem 4.560 · medium

Find \( \displaystyle \int 9 x^{2} e^{3 x} \, dx \). (Omit the constant of integration.)
  1. \[ \int 9 x^{2} e^{3 x}\, dx \]
    integralStart with the integral of the given function.✓ Proved
  2. \[ = 9 \int x^{2} e^{3 x}\, dx \]
    linearityFactor out the constant 9.✓ Proved
  3. \[ = 3 x^{2} e^{3 x} - 3 \int 2 x e^{3 x}\, dx \]
    parts algebraApply integration by parts with u = x**2 and dv = exp(3*x)dx. Distribute the 9 and simplify the fraction.✓ Proved
  4. \[ = 3 x^{2} e^{3 x} - 6 \int x e^{3 x}\, dx \]
    algebraFactor out the 2 from the integral.✓ Proved
  5. \[ = 3 x^{2} e^{3 x} - 2 x e^{3 x} + 2 \int e^{3 x}\, dx \]
    parts algebraApply integration by parts to the remaining integral with u = x and dv = exp(3*x)dx. Distribute the -6 and simplify the terms.✓ Proved
  6. \[ = 3 x^{2} e^{3 x} - 2 x e^{3 x} + \frac{2 e^{3 x}}{3} \]
    antiderivativeEvaluate the final integral.✓ Proved
  7. \[ = \left(3 x^{2} - 2 x + \frac{2}{3}\right) e^{3 x} \]
    simplifyFactor out the common exponential term.✓ Proved
Answer \( \frac{\left(9 x^{2} - 6 x + 2\right) e^{3 x}}{3} + C \)

✓ 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
5✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
6✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
7✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
8✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
9✓ 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 the stated antiderivative back to the integrand

Reviewers

  • gpt-oss:20b: pass
  • qwen3.6:27b-mlx: pass — The solution correctly applies integration by parts twice and handles algebraic simplifications in single-rule steps. All labels are appropriate and the logic is sound.
Every verdict on record (4)
  • gpt-oss:20b: pass 2026-10-07
  • qwen3.6:27b-mlx: pass 2026-10-07 — The solution correctly applies integration by parts twice and handles algebraic simplifications in single-rule steps. All labels are appropriate and the logic is sound.
  • qwen3.6:27b-mlx: pass 2026-10-07 — The solution correctly applies integration by parts twice and handles algebraic simplifications properly. Each step changes only one aspect of the expression and uses valid labels from the fixed vocabulary.
  • gpt-oss:20b: pass 2026-10-07

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 2026-10-07 with SymPy 1.14.0.