solving a quadratic equation with irrational roots

Mathematics
Tutor: None Selected Time limit: 1 Day

A ball is thrown from an initial height of 

 meter with an initial upward velocity of 
. The ball's height 
 (in meters) after 
 seconds is given by the following.
Find all values of 
 for which the ball's height is 
 meters.
Apr 30th, 2015

I have already solved this question.

Apr 30th, 2015

could you help me set it up to get the right number for the square root cause i got -751 with positive 38 but with -38 i got 769 i confuse my signs when im supposed solve the 4*ac part

A ball is thrown from a height of 

38

 meters with an initial downward velocity of 

3/ms

. The ball's height 

h

 (in meters) after 

t

 seconds is given by the following.

h=38−3t-5t2

How long after the ball is thrown does it hit the ground?Round your answer(s) to the nearest hundredth.

Apr 30th, 2015

yes


Apr 30th, 2015

thank you 

Apr 30th, 2015

here h=0

therefore,

0=38-3t-5t^2

5t^2+3t-38=0







Apr 30th, 2015

yes i understand that part putting it in the formula confuses me can you help me on that part

Apr 30th, 2015

yes compare with ax^2+bx+c=0

x=-b+-sqrt(b^2-4ac)  /2a


Apr 30th, 2015

here a=5 b=3 and c=-38

and solve

Apr 30th, 2015

D; no i understand the formulas , im asking can you plug in  the numbers so i understand if im putting my negative and positive signs right cause when i dont i get the answer wrong 

Apr 30th, 2015

okay thank youu

Apr 30th, 2015

fine thanks.

Apr 30th, 2015

3.073 and -2.473 can you round this to the hundreths place for me please 

Apr 30th, 2015

for -2.473 would i round it to be -2.5?

Apr 30th, 2015

No it cannot be rounded to 2.5 answer is -2.47

Apr 30th, 2015

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Apr 30th, 2015
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Apr 30th, 2015
May 26th, 2017
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