Question 1153181
<pre>If we plot the graph, we get

{{{drawing(64,400,-.9,4.3,-.9,25,

graph(64,400,-.9,4.3,-.9,25,(-4.9x^2 + 18x + 8)*sqrt(x)/sqrt(x)) )}}}

We use the vertex formula to find the value of t at the maximum height,
which is reached at the vertex.

{{{matrix(1,7,

(matrix(5,1,
value, of, t, at, vertex)),
 ""="",
 -b/(2a),
 ""="",
-18/(2*(-4.9)),
""="",
1.836734694

)}}}

Round to 1.837 seconds to get to the maximum height.

Edwin</pre>