∫Calc Practice

Limit of \( \displaystyle \frac{3 x - 3}{\sqrt{3 x + 1} - 2} \) as \( x \to 1 \)

Problem 1.358 · medium

Evaluate \( \displaystyle \lim_{x \to 1} \frac{3 x - 3}{\sqrt{3 x + 1} - 2} \).
  1. \[ \lim_{x \to 1^+}\left(\frac{3 x - 3}{\sqrt{3 x + 1} - 2}\right) \]
    limit factor rationalizeStart with the limit of the function as x approaches 1 from the right. Factor out the constant 3 from the numerator. Multiply the numerator and denominator by the conjugate of the denominator.✓ Proved
  2. \[ = \lim_{x \to 1^+}\left(\sqrt{3 x + 1} + 2\right) \]
    algebra simplify factor cancelExpand the denominator using the difference of squares. Simplify the expression in the denominator. Factor out the 3 from the denominator. Cancel the common factor (x - 1) from the numerator and denominator.✓ Proved
  3. \[ = 4 \]
    limitEvaluate the limit by substituting x = 1.✓ Proved
Answer \( 4 \)

✓ 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
undefined where sqrt(3*x + 1) - 2 = 0
3✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where sqrt(3*x + 1) - 2 = 0
4✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where sqrt(3*x + 1) - 2 = 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
answer✓ Provedsympy 1.14.0final line against the stated answer: simplify(a - b) reduced to 0
answer, a second way✓ Provedsympy 1.14.0SymPy took the limit from both sides and got the stated value

Reviewers

  • gpt-oss:20b: pass
  • qwen3.6:27b-mlx: pass
Every verdict on record (4)
  • gpt-oss:20b: pass 2026-10-07
  • qwen3.6:27b-mlx: pass 2026-10-07
  • qwen3.6:27b-mlx: pass 2026-10-07 — The solution correctly applies algebraic manipulation to resolve the indeterminate form, with each step changing only one aspect of the expression and using valid labels from the 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.