Please help me with this word problem. I'm stuck and I have 4 more just like it to do tonight!

A canon on the top of a cliff is fired at a target in a valley 561 ft below. The height of the cannonball above the floor of the valley can be modeled by the equation:
H(t)= -16t^2+554t+561

~Where H is the height of the cannonball above the floor of the valley, and T is the time in seconds after the cannonball is fired, How many seconds after the cannonball is fired will it be at its highest point? Round your final answer to thousandths of a second.

Question

Please help me with this word problem. I'm stuck and I have 4 more just like it to do tonight! 

A canon on the top of a cliff is fired at a target in a valley 561 ft below. The height of the cannonball above the floor of the valley can be modeled by the equation:
               H(t)= -16t^2+554t+561

~Where H is the height of the cannonball above the floor of the valley, and T is the time in seconds after the cannonball is fired, How many seconds after the cannonball is fired will it be at its highest point? Round your final answer to thousandths of a second.

jim_thompson5910 · Answer

I'm going to use x in place of t

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