Answer:
8.2secs
Step-by-step explanation:
Given the expression for calculating the height as;
h = -16x^2+127x+80
Given h = 40
Substitute
40 = -16x^2+127x+80
-16x^2+127x+80 - 40 = 0
-16x^2+127x+40 = 0
16x^2-127x-40 = 0
Factorize
x = -(-127)±√(-127)²-4(16)(-40)/2(16)
x = 127±√16,129+2,560/32
x = 127±√18,689/32
x = 127±136.71/32
x = 127+136.71/32
x = 263.71/32
x = 8.24
Hence the required time to the nearest tenth is 8.2secs
