Question 204163
 The height in meters of the cork above the level ground at time t seconds is modelled into the equaiton. h= 1+8t-5t^2
h stands for height t stands for time.
I answered some eairler questions relating to this but am stuck on this next part. 
Substitute h=1.65 into the equation h= 1+8t-5t^2, and rearrange this to the quadratic equation t^2-1.6t+0.13=0 
----------------------
1.65 = 1+8t-5t^2 gives the time that the cork is 1.65 meters above ground.
1.65 = 1+8t-5t^2
5t^2 - 8t + 0.65 = 0
You can solve for t.
*[invoke solve_quadratic_equation 5,-8,.65]
There are 2 values for t (the solver uses x) that the cork is 1.65 meters above ground.  It passes 1.65 meters going up, then again going down.