The formula of parabola vertex ordinate

The formula of parabola vertex ordinate

y=ax²+bx+c
The vertex coordinates are (- B / 2a, (4ac-b & # 178;) / 4A)
therefore
Ordinate (4ac-b & # 178;) / 4A

How to prove that the limit of (1 + 2 ^ n + 3 ^ n) ^ 1 / N is 3 with the pinch criterion

When n → + ∞
(1+2^n+3^n)^1/n>(3^n)^1/n=3
(1+2^n+3^n)^1/n

If there is always a common point between the line L and the line segment connecting a (1, - 2), B (2,1), then the value range of the slope k of the line L is______ ．

KPa = − 2 − (− 1) 1 − 0 = - 1, KPB = − 1 − 10 − 2 = 1. ∵ there is always a common point between the line L and the line segment connecting a (1, - 2), B (2,1), ∵ kPa ≤ KL ≤ KPB, ∵ 1 ≤ K ≤ 1. ∵ the slope k of the line L is [- 1,1]. So the answer is: [- 1,1]