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

#1**+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

CPhill Apr 10, 2018