Step-by-step explanation:
I believe you have mistyped the equation, but I know it’s h=−16t2+8t+80 .
When the diver jumps, the timer starts, so t=0 .
When the diver reaches the water, the height relative to the water is zero, so h=0 .
Therefore, you just have to discover the time (t) that corresponds to the moment when the diver reaches the end, in other words, when h=0 . So here we go:
0=−16t2+8t+80
Δ=b2−4ac
Δ=82−4⋅(−16)⋅80
Δ=64+5120
Δ=5184
x=−b±Δ−−√2a
x=−8±72−32
x1=−8−72−32=−80−32→x1=2.5
x2=−8+72−32=64−32→x2=−2
Since we’re looking for time, we can only pick the positive result, so the air time is 2.5 (final) - 0 (initial), which is 2.5 seconds
