Question

0=-4t^2+20t+1 i need to figure out wat t is

Answer 1

Have you learned the quadratic formula?

Answer 2

yea but dat aint working it would be a=4 b=-20 c=1 can u try

Answer 3

a = -4
b = 20
c = 1

Answer 4

yea

Answer 5

im trying 2 figure dis out

Answer 6

(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???

Answer 7

im stuck on the step with the quadratic formula

Answer 8

So what is the initial velocity?

Answer 9

Plug that in for v. What is the height above the ground? Plug that in for c.

Answer 10

v is 80

Answer 11

And c?

Answer 12

by-bye polpok

Answer 13

c is 4

Answer 14

0=-16^2+80t+4 simplified its 0=-4t^2+20t+1

Answer 15

Yep.

Answer 16

but i need t

Answer 17

Ok so using the formula for the quadratic, what is a, b, and c.

Answer 18

\[0 =at^2 + bt + c \implies t = \frac{-(b) \pm \sqrt{(b)^2 - 4(a)(c)}}{2(a)}\]

Answer 19

a=-4
b=20
c=1

Answer 20

yea but idk y i keep getting really big numbers wat do u get

Answer 21

t has 2 be 5.1s or 1s or 2s,3s

Answer 22

I got -0.049509756796392246, and 5.049509756796392

Answer 23

Are you forgetting to divide by -8?

Answer 24

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

Answer 25

Start with the part under the square root

Answer 26

so dont put -20 first

Answer 27

20*20 - 4*(-4)*(1)

Answer 28

What do you get for that part

Answer 29

416

Answer 30

Now take the square root of that

Answer 31

20.3

Answer 32

Ok, now you have 2 solutions:

\[x = \frac{-20 \pm 20.3}{2(-4)}\]

Answer 33

Oh, and you didn't round up.. I think it's 20.396 or 20.4

Answer 34

im still getting 50.75

Answer 35

-20 + 20.4 = ?
-20 - 20.4 = ?

Answer 36

2(-4) = ?

Answer 37

.4

Answer 38

-8

Answer 39

ok so u dont multiply the -20 to the 20.4/-8

Answer 40

No, you add and subtract them

Answer 41

(-20 plus or minus 20.4) / -8

Answer 42

i got -0.5

Answer 43

There's one more possibility.

Answer 44

nope i got -17.45

Answer 45

and -22.55

Answer 46

(-20 - 20.4)/-8

Answer 47

-0.05 is one option.

Answer 48

But the other one is positive

Answer 49

ok i got u now wow thanks but its weird how i cant put the whole thing in the calculator

Answer 50

Because the order matters

Answer 51

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.

Answer 52

ok can u help me wit another one

Answer 53

probably

Answer 54

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

Answer 55

So how would you set this one up?

Answer 56

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

Answer 57

i got 100t=-16t^2+80t+4

Answer 58

it's just 100, h is the height.

Answer 59

so \[100 = -16t^2 + 80t + 4\]

Answer 60

ok wat next

Answer 61

move the 100 to the other side so it equals 0 and then use the quadratic formula again.

Answer 62

by subtracting 100 from both sides that is

Answer 63

0=-4t^2+20+24

Answer 64

4-100 is -196, not positive

Answer 65

i got 3

Answer 66

err -96 rather

Answer 67

well den dis aint working now idk u do it

Answer 68

You did it right, I don't know how, but 3 is one answer. There is another answer

Answer 69

If you used -4t^2+20+24

You should have gotten (-1 and 6) though

Answer 70

But the correct formula
-4t^2+20t-24 = 0 gives one of the solutions being 3 and the other being 2

Answer 71

the answer can only be 1s or 2s,3s

Answer 72

show me ur formula

Answer 73

\[0=-4t^2 + 20t - 24 \implies t = \frac{-20 \pm \sqrt{20^2 - 4(-4)(-24)}}{2(-4)}\]

Answer 74

ok i got dat but now getting big numbers again

Answer 75

Do the part under the square root first

Answer 76

\(20^2 - 4(-4)(-24)\)

Answer 77

16

Answer 78

and the square root of 16 is?

Answer 79

4

Answer 80

Ok, and what's the denominator? 2(-4)

Answer 81

-8

Answer 82

polpak, i have some confusion. check your equation once again

Answer 83

So you have two solutions:

(-20 + 4)/-8 and (-20 - 4)/-8

Answer 84

for the first one you have -16/-8 and the second is -24/-8

Answer 85

omg thanks

Answer 86

Hrm India?

Answer 87

oh whoopse

Answer 88

No.. wait, that's right

Answer 89

ok linda dis is my question create ur own i need help 2 get off mines

Answer 90

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 \[-4t ^{2}-20t-24 \]

Answer 91

ah. ok

Answer 92

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

Answer 93

can u check the answer i get

Answer 94

i cant do \[\sqrt{-21}\]

Answer 95

so how do i do dis problem

Answer 96

it is a imaginary number!!!! it will come \[i \sqrt{21}\]

Answer 97

does dat equal -1

Answer 98

or 1