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View Full Version : !Quadratic prblem solving!


Alpha_Male81
Mar 17, 2007, 09:06 AM
I have a couple questions to ask and I really need to know them within two days:

1) WHen a projectile is fired, the vertical component of its initial velocity is such that its height h, in metres, t seconds after firing is given by h= 250t - 4.9t^2. Is it possible for the projectile to reach a height of 2.75 km? 4.0 km?

I've tried many possibilities, but I'm struggling and now time is running out so please help me.

Also

Three pieces of rod measure 20 cm, 41 cm, and 44 cm. IF the same amount is cut off each piece, the remaining lengths can be formed into a right triangle. What length is cut off?

And..

Chris cuts hald a rectangular lawn, 40m by 30m, by mowing strips of equal width around the perimeter. Jerri cuts the small rectangle left inside the area. How wide are the strips that Chris cuts if they are to share the work equally?

I need to know all the work so I can know what to do exactly, thanks a lot for your time and patience.

CaptainForest
Mar 17, 2007, 05:35 PM
Take a look at this post: https://www.askmehelpdesk.com/math-sciences/quadratic-equations-problem-solving-16727.html

His first question in post 1 is VERY similar to your first question.

Read my response, try it on your own, and post your solution and I will look it over for you.

Alpha_Male81
Mar 17, 2007, 09:31 PM
Take a look at this post: https://www.askmehelpdesk.com/math-sciences/quadratic-equations-problem-solving-16727.html

His first question in post 1 is VERY similar to your first question.

Read my response, try it on your own, and post your solution and I will look it over for you.

Yup Ive seen that question arleady and tried it out, but it actually applied to another question I was assigned. Thanks though, Im still trying to fidget around with it for this question, but still no luck. I'll keep trying but thanks for that piece of info

galactus
Mar 18, 2007, 08:44 AM
Three pieces of rod measure 20 cm, 41 cm, and 44 cm. IF the same amount is cut off each piece, the remaining lengths can be formed into a right triangle. What length is cut off?


Here's a hint: Let x equal the amount cut from each and use Pythagoras. You will end up with a quadratic. Solve it for x. One solution will be extraneous. The right one will be obvious.

Alpha_Male81
Mar 18, 2007, 04:59 PM
I ended up getting a variety of answers, but I kept on playing around with the problem until I got:

x= - 1/9.8 , -499/9.8

I'm not sure if that's right, but that's one of the possibilities I got

galactus
Mar 18, 2007, 06:43 PM
No, No. You can't have a negative length.

(20-x)^{2}+(41-x)^{2}=(44-x)^{2}