Question 1182237
*[illustration problem1.png].
<pre>
Replace h by 8 and solve for t:

{{{h=4+18t-16t^2}}}

{{{8=4+18t-16t^2}}}

{{{16t^2-18t+4=0}}}

Use the quadratic formula to finish:

{{{t = (-b +- sqrt( b^2-4*a*c ))/(2*a) }}}

If you get stuck, I'll help you.  Tell me
in the message space below.

Edwin</pre>