Limit of \( \displaystyle \frac{3 x - 3}{\sqrt{3 x + 1} - 2} \) as \( x \to 1 \)
Problem 1.358 · medium
Evaluate \( \displaystyle \lim_{x \to 1} \frac{3 x - 3}{\sqrt{3 x + 1} - 2} \).
- \[ \lim_{x \to 1^+}\left(\frac{3 x - 3}{\sqrt{3 x + 1} - 2}\right) \]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
- \[ = \lim_{x \to 1^+}\left(\sqrt{3 x + 1} + 2\right) \]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
- \[ = 4 \]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
| 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 undefined where sqrt(3*x + 1) - 2 = 0 |
| 3 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where sqrt(3*x + 1) - 2 = 0 |
| 4 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where sqrt(3*x + 1) - 2 = 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 |
| 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 took the limit from both sides and got the stated value |
Reviewers
gpt-oss:20b: passqwen3.6:27b-mlx: pass
Every verdict on record (4)
gpt-oss:20b: pass 2026-10-07qwen3.6:27b-mlx: pass 2026-10-07qwen3.6:27b-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.