Limit of \( \displaystyle \frac{2 x - 3}{\sqrt{2 x + 1} - 2} \) as \( x \to \frac{3}{2} \)
Problem 1.142 · medium
Evaluate \( \displaystyle \lim_{x \to \frac{3}{2}} \frac{2 x - 3}{\sqrt{2 x + 1} - 2} \).
- \[ \lim_{x \to \frac{3}{2}^+}\left(\frac{2 x - 3}{\sqrt{2 x + 1} - 2}\right) \]limit algebraIdentify the limit to evaluate. Multiply the numerator and denominator by the conjugate.✓ Proved
- \[ = \lim_{x \to \frac{3}{2}^+}\left(\sqrt{2 x + 1} + 2\right) \]algebra simplify cancelExpand the denominator using the difference of squares. Simplify the denominator. Cancel the common factor (2*x - 3).✓ Proved
- \[ = 4 \]limit algebra simplify simplify simplifyEvaluate the limit by substituting x = 3/2. Simplify the expression inside the square root. Calculate the square root. Evaluate the square root. Final result.✓ 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(2*x + 1) - 2 = 0 |
| 3 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where sqrt(2*x + 1) - 2 = 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 |
| 10 | ✓ 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)
qwen3.6:27b-mlx: pass 2026-10-04gpt-oss:20b: pass 2026-10-04qwen3.6:27b-mlx: pass 2026-10-04 — The solution correctly applies the conjugate method to resolve the indeterminate form. Each step changes only one aspect of the expression and uses valid labels from the fixed vocabulary.gpt-oss:20b: pass 2026-10-04
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 2026-10-04 with SymPy 1.14.0.