[機統] Casella書中的一段

[Jer1983 (stanley)]

Statistical inference 2ed, p.172

在證明 Theorem 4.5.7 的時候, 中間有一段話:

"This quadratic function of t is greater than ... ...
Thus, this quadratic function can have at most one real root and
thus must have a nonpositive discriminant."

請問這段話背後的關係式是如何推導出來的呢? thanks

我想問的是Thus之後的這一段.
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◆ From: 140.122.101.130
→ forloricever:就在你的 since ... 處, h(t) non-negative
※ 編輯: Jer1983         來自: 140.122.101.130      (08/24 13:22)
→ forloricever:h(t) 二次函數, 拋物線開口向上, 非負, 判別式 <= 0
→ forloricever:想要問的是這個嗎?
→ Jer1983     :為什麼can have at most one real root?
→ Jer1983     :以及為什麼must have a nonpositive discriminant?
→ LITTLEN     :一樓解答了...
→ Jer1983     :我真的忘了相關的定理...再多一點提示好嗎^^
→ forloricever:http://ppt.cc/e9CD