SOLUTION: Hello, I wanted to see if I was doing this problem correctly. I started the answer with -16t^2+16t+410=90, then subtracted 90 to get -16t^2+16t+320=0 and then perform the qua

Question 682133: Hello,
I wanted to see if I was doing this problem correctly.
I started the answer with -16t^2+16t+410=90, then subtracted 90 to get -16t^2+16t+320=0 and then perform the quadratic equation to get the answer. Is this the right start?

The function h(t) = -16^2+16t+410 gives the height h, in feet, of a coin tossed upward from a balcony 410 ft high with an initial velocity of 16 ft/sec. During what interval of time will the coin be at a height of at least 90 ft?
Thanks
Answer by nerdybill(7384) (Show Source): You can put this solution on YOUR website!
I started the answer with -16t^2+16t+410=90, then subtracted 90 to get -16t^2+16t+320=0 and then perform the quadratic equation to get the answer. Is this the right start?
Yes, applying the "quadratic equation" is one approach.
But, you could have "factored" it (an easier approach):
-16t^2+16t+320=0
dividing both sides by -16:
t^2-t-20=0
factoring:
(t+4)(t-5) = 0
t = {-4, 5}
throw away the negative solution (extraneous) leaving:
t = 5 seconds
.

RELATED QUESTIONS
A foul ball leaves a bat, hits home plate, and travels straight up with an initial... (answered by stanbon,Earlsdon)

Hi! i wanted to see if the answer i got for this problem was right. The quadratic... (answered by Earlsdon)

Hello. I'm checking to see if I did this problem correctly using the quadratic formula (answered by jim_thompson5910)

Problem I need to see if I am doing correctly (3^2... (answered by ReadingBoosters)

An object projected from height of 48 ft. with an initial velocity of 32 ft./sec after t... (answered by KMST)

The text asks us to solve the following statements using either the "object dropped" or... (answered by stanbon,Earlsdon)

I need to know if I solved this correctly. I came up with this answer. 8(2t+1)>4(7t+7)... (answered by robertb,mananth)

hello i just wanted to check to see if I was doing this word problem correctly. The word... (answered by Edwin McCravy)

4log{{{2}}}x + log{{{2}}}5 = log{{{2}}}405 What is the value of X in this logarithm? When (answered by AnlytcPhil)