Solving a Quadratic Equation

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In the College Algebra Section for Graphing Functions, Question 26:

I really need help with the detail of solving this problem. Can someone please show me the step by step process in figuring out this problem? I have tried to calculate it many times and cannot for the life of me come up with the correct answer.

I am familiar with the quadratic formula but for some reason cannot get it to work for this problem, I am sure that I am missing a step.

“An object is thrown directly upward from a starting height of 25 ft and a starting velocity of 85 ft per second. The following function describes the height of the object with respect to the time, t.”

h(t) = -16t2 + 85t + 25

How long does it take before the object reaches the ground? Round you answer to the nearest hundredths place.

The answer is 5.59.