anonymous
  • anonymous
0=-4t^2+20t+1 i need to figure out wat t is
Mathematics
  • Stacey Warren - Expert brainly.com
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SOLVED
At vero eos et accusamus et iusto odio dignissimos ducimus qui blanditiis praesentium voluptatum deleniti atque corrupti quos dolores et quas molestias excepturi sint occaecati cupiditate non provident, similique sunt in culpa qui officia deserunt mollitia animi, id est laborum et dolorum fuga. Et harum quidem rerum facilis est et expedita distinctio. Nam libero tempore, cum soluta nobis est eligendi optio cumque nihil impedit quo minus id quod maxime placeat facere possimus, omnis voluptas assumenda est, omnis dolor repellendus. Itaque earum rerum hic tenetur a sapiente delectus, ut aut reiciendis voluptatibus maiores alias consequatur aut perferendis doloribus asperiores repellat.
chestercat
  • chestercat
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anonymous
  • anonymous
Have you learned the quadratic formula?
anonymous
  • anonymous
yea but dat aint working it would be a=4 b=-20 c=1 can u try
anonymous
  • anonymous
a = -4 b = 20 c = 1

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anonymous
  • anonymous
yea
anonymous
  • anonymous
im trying 2 figure dis out
anonymous
  • anonymous
(h(t)=-16t^2+vt+c where h is the approximate height in ft t is the time in motion in seconds v is the initial upward velocity in ft per second and c is the initial height in ft) A baseball player hits a pitched ball when it is 4ft above the ground the initial upward velocity is 80ft/s how long will it take for the ball to hit the ground???
anonymous
  • anonymous
im stuck on the step with the quadratic formula
anonymous
  • anonymous
So what is the initial velocity?
anonymous
  • anonymous
Plug that in for v. What is the height above the ground? Plug that in for c.
anonymous
  • anonymous
v is 80
anonymous
  • anonymous
And c?
anonymous
  • anonymous
by-bye polpok
anonymous
  • anonymous
c is 4
anonymous
  • anonymous
0=-16^2+80t+4 simplified its 0=-4t^2+20t+1
anonymous
  • anonymous
Yep.
anonymous
  • anonymous
but i need t
anonymous
  • anonymous
Ok so using the formula for the quadratic, what is a, b, and c.
anonymous
  • anonymous
\[0 =at^2 + bt + c \implies t = \frac{-(b) \pm \sqrt{(b)^2 - 4(a)(c)}}{2(a)}\]
anonymous
  • anonymous
a=-4 b=20 c=1
anonymous
  • anonymous
yea but idk y i keep getting really big numbers wat do u get
anonymous
  • anonymous
t has 2 be 5.1s or 1s or 2s,3s
anonymous
  • anonymous
I got -0.049509756796392246, and 5.049509756796392
anonymous
  • anonymous
Are you forgetting to divide by -8?
anonymous
  • anonymous
tell me exactly how 2 put it in my calculator cuz everytime i do i get large #'s and yes i put divide y -8
anonymous
  • anonymous
Start with the part under the square root
anonymous
  • anonymous
so dont put -20 first
anonymous
  • anonymous
20*20 - 4*(-4)*(1)
anonymous
  • anonymous
What do you get for that part
anonymous
  • anonymous
416
anonymous
  • anonymous
Now take the square root of that
anonymous
  • anonymous
20.3
anonymous
  • anonymous
Ok, now you have 2 solutions: \[x = \frac{-20 \pm 20.3}{2(-4)}\]
anonymous
  • anonymous
Oh, and you didn't round up.. I think it's 20.396 or 20.4
anonymous
  • anonymous
im still getting 50.75
anonymous
  • anonymous
-20 + 20.4 = ? -20 - 20.4 = ?
anonymous
  • anonymous
2(-4) = ?
anonymous
  • anonymous
.4
anonymous
  • anonymous
-8
anonymous
  • anonymous
ok so u dont multiply the -20 to the 20.4/-8
anonymous
  • anonymous
No, you add and subtract them
anonymous
  • anonymous
(-20 plus or minus 20.4) / -8
anonymous
  • anonymous
i got -0.5
anonymous
  • anonymous
There's one more possibility.
anonymous
  • anonymous
nope i got -17.45
anonymous
  • anonymous
and -22.55
anonymous
  • anonymous
(-20 - 20.4)/-8
anonymous
  • anonymous
-0.05 is one option.
anonymous
  • anonymous
But the other one is positive
anonymous
  • anonymous
ok i got u now wow thanks but its weird how i cant put the whole thing in the calculator
anonymous
  • anonymous
Because the order matters
anonymous
  • anonymous
Plus plugging the whole thing in at once makes it harder to find where you made your mistake. Just put in each piece at a time.
anonymous
  • anonymous
ok can u help me wit another one
anonymous
  • anonymous
probably
anonymous
  • anonymous
using the same formula a flare is launched from the deck of a life boat 4ft above the water surface the initial upward velocity is 80ft/s after how many seconds will the flare be 100 ft above the water surface
anonymous
  • anonymous
So how would you set this one up?
anonymous
  • anonymous
h(t)=-16t^2+vt+c where h is the approximate height in ft t is the time in motion in seconds v is the initial upward velocity in ft per second and c is the initial height in ft
anonymous
  • anonymous
i got 100t=-16t^2+80t+4
anonymous
  • anonymous
it's just 100, h is the height.
anonymous
  • anonymous
so \[100 = -16t^2 + 80t + 4\]
anonymous
  • anonymous
ok wat next
anonymous
  • anonymous
move the 100 to the other side so it equals 0 and then use the quadratic formula again.
anonymous
  • anonymous
by subtracting 100 from both sides that is
anonymous
  • anonymous
0=-4t^2+20+24
anonymous
  • anonymous
4-100 is -196, not positive
anonymous
  • anonymous
i got 3
anonymous
  • anonymous
err -96 rather
anonymous
  • anonymous
well den dis aint working now idk u do it
anonymous
  • anonymous
You did it right, I don't know how, but 3 is one answer. There is another answer
anonymous
  • anonymous
If you used -4t^2+20+24 You should have gotten (-1 and 6) though
anonymous
  • anonymous
But the correct formula -4t^2+20t-24 = 0 gives one of the solutions being 3 and the other being 2
anonymous
  • anonymous
the answer can only be 1s or 2s,3s
anonymous
  • anonymous
show me ur formula
anonymous
  • anonymous
\[0=-4t^2 + 20t - 24 \implies t = \frac{-20 \pm \sqrt{20^2 - 4(-4)(-24)}}{2(-4)}\]
anonymous
  • anonymous
ok i got dat but now getting big numbers again
anonymous
  • anonymous
Do the part under the square root first
anonymous
  • anonymous
\(20^2 - 4(-4)(-24)\)
anonymous
  • anonymous
16
anonymous
  • anonymous
and the square root of 16 is?
anonymous
  • anonymous
4
anonymous
  • anonymous
Ok, and what's the denominator? 2(-4)
anonymous
  • anonymous
-8
anonymous
  • anonymous
polpak, i have some confusion. check your equation once again
anonymous
  • anonymous
So you have two solutions: (-20 + 4)/-8 and (-20 - 4)/-8
anonymous
  • anonymous
for the first one you have -16/-8 and the second is -24/-8
anonymous
  • anonymous
omg thanks
anonymous
  • anonymous
Hrm India?
anonymous
  • anonymous
oh whoopse
anonymous
  • anonymous
No.. wait, that's right
anonymous
  • anonymous
ok linda dis is my question create ur own i need help 2 get off mines
anonymous
  • anonymous
no, its alright now. i don't how but the latex code was not properly loaded and the \[-4t ^{2}+20t-24 \] was looking like \[-4t ^{2}-20t-24 \]
anonymous
  • anonymous
ah. ok
anonymous
  • anonymous
a basketball player shoots the ball with an initial velocity of 20ft/s the ball is 6ft above the floor wen it leaves her hands how long will it take for the ball to reach the rim of the basket 10 ft above th floor on its way down
anonymous
  • anonymous
can u check the answer i get
anonymous
  • anonymous
i cant do \[\sqrt{-21}\]
anonymous
  • anonymous
so how do i do dis problem
anonymous
  • anonymous
it is a imaginary number!!!! it will come \[i \sqrt{21}\]
anonymous
  • anonymous
does dat equal -1
anonymous
  • anonymous
or 1
anonymous
  • anonymous
\[-1 = i ^{2}\]
anonymous
  • anonymous
i=1 right
anonymous
  • anonymous
no, it ain't right. i is nothing but an imaginary number. it can not be solved. it has to be written i only.
anonymous
  • anonymous
well it has 2 be possible cuz there is no i answer on dis paper
anonymous
  • anonymous
one thing, time can't be negative.
anonymous
  • anonymous
your solution seems wrong!!!
anonymous
  • anonymous
i have 0=-4t^+5-1
anonymous
  • anonymous
\[-4t ^{5}-1\]
anonymous
  • anonymous
do you want to write this equation???
anonymous
  • anonymous
my bad 0=-4^2+5-1
anonymous
  • anonymous
i know the answer has 2 be 1 or 1.65 but idk y it aint working
anonymous
  • anonymous
still something wrong in the equation. there is no "t"
anonymous
  • anonymous
0=-4t^2+5t-1
anonymous
  • anonymous
yes, the equation is giving t = 1 and o.5
anonymous
  • anonymous
how uget dat did u use the quadratic formula
anonymous
  • anonymous
hmm, yes
anonymous
  • anonymous
how cuz i got -41/-8 + or - 5
anonymous
  • anonymous
you must be wrong cuz i used calculator to solve.
anonymous
  • anonymous
i did 2 show me wat u put in
anonymous
  • anonymous
\[\frac{-b \pm\sqrt{b^2-4ac}}{2a}\]
anonymous
  • anonymous
i know dat wat numbers did u end up wit
anonymous
  • anonymous
1 and 0.5
anonymous
  • anonymous
will be the answer
anonymous
  • anonymous
no i mean like wat was b^2-4ac
anonymous
  • anonymous
0=-4t^2+5t-1 put a = -4 b = 5 and c = -1
anonymous
  • anonymous
i did i keep getting -41 on top
anonymous
  • anonymous
\[b ^{2}-4ac = 5^{2}-4(-4)(-1)\]
anonymous
  • anonymous
you will get 9
anonymous
  • anonymous
i was putting -5^2
anonymous
  • anonymous
-5^2 will also be 25. the sign doesn't matter when there is a square
anonymous
  • anonymous
thanks
anonymous
  • anonymous
my pleasure!!!
anonymous
  • anonymous
0=-16t^2+27+1 need some help

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