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Limit of \( \displaystyle \frac{2 x + \left(2 x - 1\right)^{2} - 7}{2 x - 3} \) as \( x \to \frac{3}{2} \)

Problem 1.140 · medium

Evaluate \( \displaystyle \lim_{x \to \frac{3}{2}} \frac{2 x + \left(2 x - 1\right)^{2} - 7}{2 x - 3} \).
  1. \[ \lim_{x \to \frac{3}{2}^+}\left(\frac{2 x + \left(2 x - 1\right)^{2} - 7}{2 x - 3}\right) \]
    limitStarting with the limit of the function at x = 3/2.✓ Proved
  2. \[ = \lim_{x \to \frac{3}{2}^+}\left(\frac{4 x^{2} - 2 x - 6}{2 x - 3}\right) \]
    algebra simplify factorExpand the squared term. Combine like terms in the numerator. Factor out a 2 from the numerator.✓ Proved
  3. \[ = \lim_{x \to \frac{3}{2}^+}\left(\frac{\left(x + 1\right) \left(4 x - 6\right)}{2 x - 3}\right) \]
    factorFactor the quadratic expression in the numerator.✓ Proved
  4. \[ = \lim_{x \to \frac{3}{2}^+}\left(2 x + 2\right) \]
    cancel simplifyCancel the common factor (2*x - 3). Distribute the 2.✓ Proved
  5. \[ = 5 \]
    substitution algebra limitSubstitute x = 3/2 into the expression. Multiply 2 by 3/2. Final evaluation of the limit.✓ Proved
Answer \( 5 \)

✓ 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 2*x - 3 = 0
3✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where 2*x - 3 = 0
4✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where 2*x - 3 = 0
5✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where 2*x - 3 = 0
6✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where 2*x - 3 = 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
10✓ 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 — The solution correctly expands, factors, cancels, and substitutes to evaluate the limit. Each step applies a single rule and is labeled correctly.
Every verdict on record (4)
  • qwen3.6:27b-mlx: pass 2026-10-04 — The solution correctly expands, factors, cancels, and substitutes to evaluate the limit. Each step applies a single rule and is labeled correctly.
  • gpt-oss:20b: pass 2026-10-04
  • qwen3.6:27b-mlx: pass 2026-10-04
  • 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.