Quick Homework Help

# 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. First question: Solve: y=3n2-6n 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                                                                          n=0      n=2  Next question: 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.  ⚑ Flag

by Ironhawk893 at November 17, 2011