Question 1172181
The 5 represents the diving board's height in m; the 8t is the speed leaving the board in m/sec and the -4.9 is the acceleration of gravity.
maximum height is at t=-b/2a or -8/-9.8 or 0.816 seconds
His maximum height was 8.27 m (I didn't round until the end). This is f(0.816)
he was in the air until h(t)=0 with positive t (the parabola has a negative t which is ignored)
rewrite as 4.9t^2-8t-5=0 (easier to deal with)
t=(1/9.8)(8+/-sqrt(64+98)) sqrt (162)=12.73 
t=2.12 sec. in the air.

{{{graph(300,300,-2,3,-5,10,8.27,-4.9x^2+8x+5)}}}