Function checkRadical

src/compute-engine/boxed-expression/factor.ts:345–357

(expr: Expression)

    }

    const sqrt = extractSquareRoot(absTerm);
    if (sqrt === null) return null;

    results.push({ sqrt, isNegative: isNeg });
  }

  // We need exactly one positive and one negative square
  const posSquares = results.filter((r) => !r.isNegative);
  const negSquares = results.filter((r) => r.isNegative);

  if (posSquares.length !== 1 || negSquares.length !== 1) return null;

  const a = posSquares[0].sqrt;
  const b = negSquares[0].sqrt;

  // Pattern: a² - b² = (a-b)(a+b)