Needing a hand here I have a couple questions for Solving Quadratic Equations with Factoring.
In the booklet they give examples but I still don't get it and maybe someone can show me an easier way or different approach to doing it. I don't know maybe I am missing something simple. I will show exactly the way it is in my book.
Step# 1 factor the quadratic equation 3n2-6n=3n(n-2)
Step# 2 set each factor that contains a variable equal to zero 3n=0 and n-2=0
Step# 3 solve for xfor each equation in Step#2 3n=0 n-2=0
A rock is thrown straight down from a building 95 meters high. The relation h= -5t2 - 25t + 95 is a model that gives the approximate height of the rock h, in meters, at t seconds after it is thrown. How long does it take the rock to reach a ledge 25 meters from the base of the building?
Solution: h = -5t2 - 25t + 95
20 = -5t2 - 25t + 95
20 - 20 = -5t2 - 25t + 95 - 20
0 = -5(t2 + 5t - 14)
0 = -5(t + 7)(t - 2)
t - 2 = 0 and t + 7 = 0
t = 2 t = -7
Therefore the roots of t = 2 and t = -7
Since you cannot have negative time (-7 seconds) the rock reaches a height of 25 meters at 2 seconds.
Where do these 20s come from I am lost with this it's the only example in the book.