+0  
 
+3
72
1
avatar+1107 

Amir stands on a balcony and throws a ball to his dog, who is at ground level.

The ball's height (in meters above the ground), x seconds after Amir threw it, is modeled by:

 

\(h(x)=-(x+1)(x-7) \)

 

How many seconds after being thrown will the ball reach its maximum height?

MathPeacock  Apr 10, 2018
edited by MathPeacock  Apr 10, 2018
 #1
avatar+86871 
+2

h(x)  =  - ( x+ 1) ( x - 7)   simpliy

 

- (x^2 - 6x - 7)  =

 

-x^2 + 6x + 7

 

In the form -x^2 + bx + c     the number of seconds to reach ax height  is given by :

 

-b / (2 * -1)   ...so we have

 

-6 / ( 2 * -1)  =   - 6 / -2   =   3 seconds

 

This graph confirms this  : https://www.desmos.com/calculator/x2ghsrm5tb

 

 

cool cool cool

CPhill  Apr 10, 2018

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