## ladiesman217 2 years ago i give medals and fans

If a baseball player hits a baseball from 4 feet off the ground with an initial velocity of 64 feet per second, how long will it take the baseball to hit the ground? Use the equation $h=-16t ^{2}+64t+4$

2. mukushla

baseball hits the ground when $$h=0$$.

ok

$$h=-16t^2 +64t +4$$ when h=0,(the ball hits the ground) $$0=-16t^2 +64t +4$$ use the general formula. what did u get?

6. sami-21

you need to solve the quadratic equation since h=0 so -16t^+64t+4=0 or 16t^2-64t-4=0 use quadratic formula with a=16 b=-64 c=-4 you will get two roots t=4 sec t=-0.6 but time cannot be negative so neglect the negative value t=4 sec is the required time .

$\frac{ -64\sqrt{64^{2}+16*-4} }{ 2*16 }$ $\frac{ -64\sqrt{64^{2}-64} }{ 32 }$

8. sami-21

it should be +64 outside the root because b=-64 and there is minus in the formula too .

note: it's $$-64 \pm \sqrt{64^2 - (4)(-16)(4)}$$ up there.

10. sami-21

correct formula is $\Large =\frac{-b \pm \sqrt{b^2-4ac}}{2a}$

$\frac{ 64\sqrt{64^{2}+256} }{32}$

12. sami-21

you miseed plus minus sign :)

yup! simplify and you're done (i guess the editor don't have it. the latex is \pm

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