Question

Please help.

Answer 1

we have

$y=-16t^{2} +120$

we know that

When the apple hit the ground the value of y is equal to zero

so

Find the x-intercept of the function

equate the function to zero

$-16t^{2} +120=0$

Group terms that contain the same variable, and move the constant to the opposite side of the equation

$-16t^{2} =-120$

$t^{2} =-120/-16$

$t^{2} =7.5$

$t=(+/-)\sqrt{7.5}$

$t=(+/-)2.74$

therefore

the answer is

$2.74\ sec$

using a graphing tool

see the attached figure to better understand the problem