题目

二次方程 函数
The following function gives the height,h metres,of a batted baseball as a function of the time,t seconds,since the ball was hit:
h= -6(t-2.5)^2+ 38.5
a) How many seconds after it was hit did the ball hit the ground ,to the nearest second?
请列出主要的演算步骤和式子.

提问时间：2020-10-13

答案

题目意思是当t=?时,t为整数,表达式-6(t-2.5)^2+ 38.5与0最接近.令-6(t-2.5)^2+ 38.5=0求出两根,分别为5.0331和-0.0331,在两根旁取三点,即0,5,6,分别代入原表达式中当t=0,表达式为 1；当t=5,表达式为 1；当t=6,表达式...