✔ 最佳答案
令 u = y² + 6
(y + 1)(y + 2)(y + 3)(y + 6) ‒ 3y*y
= [(y + 1)(y + 6)] [(y + 2)(y + 3)] ‒ 3y²
= (y² + 7y + 6)(y² + 5y + 6) ‒ 3y²
= [(y² + 6) + 7y] [(y² + 6) + 5y] ‒ 3y²
= (u + 7y)(u + 5y) ‒ 3y²
= u² + 12uy + 35y² ‒ 3y²
= u² + 12uy + 32y²
= (u + 4y)(u + 8y)
= (y² + 4y + 6)( y² + 8y + 6)