Question

Anybody able to solve 25=-4.9t^2 + 23.4t +1.3? pleasee?

Answer 1

ick!

Answer 2

its too hard to factor and the quadratic forula doesnt seem to work..

Answer 3

The quadratic formula should work. What happens when you try it?

Answer 4

maybe start with
\[0 = -4.9 t^2+23.4 t-23.7\] and then
\[49t^2-234t+237=0\] and then the quadratic formula

Answer 5

quadratic formula is a formula . it always works

Answer 6

cheat
http://www.wolframalpha.com/input/?i=49t2%E2%88%92234t%2B237%3D0

Answer 7

what would you then do with the roots you get ? i got 0.86 and -5.6 mabye my math is wrong?

Answer 8

Those can be valid roots. Just because they're not integers doesn't mean they're not valid roots.

Answer 9

or if you just need a numerical answer cheat even easier
http://www.wolframalpha.com/input/?i=25%3D-4.9t^2+%2B+23.4t+%2B1.3

Answer 10

Also, if this is for a story problem where t represents time, you can usually throw out the negative root and just use the positive root. Depends on the problem.

Answer 11

the original question was how long is the baseball above 25 meters, with the equation h=-4.9t^2 +23.4t +1.3 if that makes any more sense . h=height in m, t =time

Answer 12

yeah that is fine. between the two zeros it is above 25

Answer 13

so the zeros i got make sense?

Answer 14

from about 1.46 second to about 3.32 seconds or if it really asks "how long" then 3.32-1.46 whatever that is

Answer 15

@ladybug you have the right idea but your zeros are wrong

Answer 16

alright so i just have to redo my math?

Answer 17

The zeros you got could make sense, but don't appear to with the story given.

Try breaking it down again with the quadratic formula. For 25=-4.9t^2 + 23.4t +1.3, You'll want to egt rid of the 25 first, so it should be 0=-4.9t^2 + 23.4t -23.7.

A = -4.9
B = 23.4
C = -23.7

Answer 18

yes i did do that! somwhere from then after i messed up?

Answer 19

Show us your next step and we'll go through it here just to be sure.

Answer 20

-23=+/- sqr root of 23.4^2 -4(-4.9)(23.7)

Answer 21

just a suggestion that it makes life easier to deal with whole numbers and positive leading coefficient (not that it really matters) and i would solve
\[49t^2-234t+237=0\]

Answer 22

then add the decimals in after? because this is sosmthing im handing in for marks lol

Answer 23

no no, don't put them back in. just do the calculation with whole numbers might be easier is all

Answer 24

oh okay!

Answer 25

because you have something set equal zero, ten times it is zero as well. you will get the same answer as you would working with decimals, it just might be easier to use whole numbers. your choice

Answer 26

oh i see makes sence thankyou!