Respuesta :
Answer:
4.0616 seconds approximately
Step-by-step explanation:
We are looking for how long it takes the ball to hit the ground. h is 0 then.
So we are looking to solve -16t^2+64t+4=0
Divide both sides by -4 to make the numbers a little simpler to work with.
4t^2-16t-1=0
You could aim for completing the square or quadratic formula here.
I'm going for quadratic formula.
a=4
b=-16
c=-1
So the discriminant=b^2-4ac=(-16)^2-4(4)(-1)=16^2+16=16(16+1)=16(17)=272
You could have just put (-16)^2-4(4)(-1) into your calculator.
The quadratic formula says to do:
-b plus or minus square root (discriminant)
-------------------------------------------------------------
2 times a
=
16 plus or minus sqrt(272)
-------------------------------------
8
=(approximately)
16 plus or minus 16.4924
-----------------------------------
8
=
16+16.4924 16-16.4924
---------------- or ----------------
8 8
=
32.4924 -0.4924
------------- or -----------
8 8
=
4.0616 or -0.062
So the baseball hits the ground 4.0616 seconds approximately after the ball has been hit.
