**Re: word problems**
I have this problem that I can't get. If s=negative t^2 plus 5t plus 500, and Jery has climbed a mountain that is 500ft waiten on Jane. He throws rocks off the side waiten for her to come.How long does it take for the rock to hit the water ? If 15 sec have gone by what is the height of the rock from the water? what is the highest point the rock will go by? s= distance in feet and t= time in seconds.

s= -t^2 plus 5t plus 500

If we are working in units of feet and seconds, The general equation should be

s = -16t^2 + (v1)t + s1

where v1 is the initial velocity (for example, when we throw the rock instead of just dropping it), and s1 is the initial height (in this case 500 feet). Are you sure you have stated the problem exactly as it appears in your book?

To answer the first question, you must recognize that the height of the rock when it reaches the water is zero, i.e., s = 0. Put 0 in for s, then solve for t.

To answer the second question, put in 15 for t and find out what s equals.

To answer the third question, you must recognize that this equation will graph as a parabola that opens downward. The vertex of the parabola is where the rock is at its peak height. In other words, you must find the vertex of the parabola.

Please respond, showing all your work.