Solving Problems Involving Quadratic Relations.

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• November 13th 2011, 04:23 PM
danman
Solving Problems Involving Quadratic Relations.
its on quadratic relations and different forms ie. standard factored vertex exc all word problems (there are 3 questions)
Looking for someone to do this out of generosity
Big Pics

I dont know if these answers are right, feel free to correct me on them.
http://i.imgur.com/55Lk4.jpg
http://i.imgur.com/TOdHi.jpg
• November 13th 2011, 05:05 PM
Quacky
Re: Solving Problems Involving Quadratic Relations Help Please
Is this something upon which you are being assessed?
• November 13th 2011, 05:26 PM
danman
Re: Solving Problems Involving Quadratic Relations Help Please
No this is a test review and i need help understand these questions because the test is on monday (tommorow)
• November 13th 2011, 05:44 PM
Quacky
Re: Solving Problems Involving Quadratic Relations Help Please
Well we have:

$h=-0.04(d-19)^2+14.4$
1) Is fine except that I would advise you to label the points of intersection with the axis.
Your factors are correct. The distance is correct.You're missing a minus sign on the $ax^2+bx+c=0$ form.

Moving onto 2: The rocket will hit the ground when $h=0$

Can you solve
$-4.9t^2+44.1t=0$? Take out a common factor of $t$ and then solve.

For the max height, why not put the equation into vertex form? Alternatively, it will be the point halfway between the x-intercepts, so you could find this point and then substitute it into the formula.

I don't feel like the COMM part is something I can answer without knowing what exactly the examiners are looking for in an answer - for that, I'd consult a teacher.
• November 13th 2011, 06:00 PM
danman
Re: Solving Problems Involving Quadratic Relations Help Please
I have fixed number 1, but i am still confused for #2 on how to remove the common factor then solve. If you can further explain 2 than i should be able to turn it into factored form. As for communications mark that does not matter on this, it will matter on the actual test.
• November 13th 2011, 06:03 PM
Quacky
Re: Solving Problems Involving Quadratic Relations Help Please
$-4.9t^2+44.1t=0$

Divide both sides by $4.9$:

$-t^2+9t=0$

$t(9-t)=0$
• November 13th 2011, 06:10 PM
danman
Re: Solving Problems Involving Quadratic Relations Help Please
Once i do that do i FOIL so it will equal http://latex.codecogs.com/gif.latex?9t+t%5E2 ?
• November 13th 2011, 06:16 PM
Quacky
Re: Solving Problems Involving Quadratic Relations Help Please
The equation marks the flight path of a rocket. We already know the equation of the quadratic, which is the height, h(t) relates to the time, t, in seconds after launch. The equation is $h(t)=-4.9t^2+44.1t$. The height will be $0$ when $h(t)=0$ so you are being asked to solve

$0=-4.9t^2+44.1t$
I noticed a common factor of $4.9$ (knowing my $4.9$ times table has helped immeasurably in life) so divided through both sides by $4.9$. This gave:

$0=-t^2+9t$
There is now a common factor of t, which can be factored:
$t(-t+9)=0$
By the null factor law, there are only two ways this can be possible: if $t=0$ or if $-t+9=0$
• November 13th 2011, 06:23 PM
danman
Re: Solving Problems Involving Quadratic Relations Help Please
Ok, but once i get http://latex.codecogs.com/png.latex?t%28-t+9%29=0 What is the next step? because if http://latex.codecogs.com/png.latex?t=0 or http://latex.codecogs.com/png.latex?-t+9=0 than i dont know how to get there.
• November 13th 2011, 06:26 PM
Quacky
Re: Solving Problems Involving Quadratic Relations Help Please
If you cannot solve:
$-t+9=0$, then I am incredibly concerned about your test tomorrow! Can you not see that this means $t=9$?
• November 13th 2011, 06:33 PM
danman
Re: Solving Problems Involving Quadratic Relations Help Please
No i did not see this because i have not done it this exact way before, the teacher does not explain these kinds of things well which is why i have to come online to get the help required.
• November 13th 2011, 06:35 PM
Quacky
Re: Solving Problems Involving Quadratic Relations Help Please
Ok. What about part b? Can you put the quadratic into vertex form? (Which is the form it was in at the start of q1)
• November 13th 2011, 07:00 PM
danman
Re: Solving Problems Involving Quadratic Relations Help Please
Im not sure if i did it right but i got 793.8m on for b.

I have to go to bed now so i wont be able to correct it right now if its wrong.
• November 13th 2011, 07:07 PM
Quacky
Re: Solving Problems Involving Quadratic Relations Help Please
I think you really need to talk to someone because the problems you're having will take time to correct and can't be rectified over a quick forums session. Either talk to a parent or the teacher or find a tutor or study group because obviously you're not taking in the information that you require, and it's probably not your fault but it is up to you to control it. I would try to tell the teacher there are problems before starting the test tomorrow - he will understand. And he can either find out from you, or from a failed test paper and I think honestly, it will help you a lot in the long run to have a talk with him.
• November 13th 2011, 07:09 PM
danman
Re: Solving Problems Involving Quadratic Relations Help Please
Yes my school does have a student help room for math so im most likely going to go to that. Im one of those people who understand it when its taught but forget when i try to do it, the teacher just does not continually do the same questions and moves on too quick. I am not the only person who thinks this, the class average is failing.
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