Math Is Fun Forum

Marquis de Saint-Loup

Guest

Algebra q

Hello! I'm working on a problem which has me befuddled, and was hoping someone a bit more mathematically knowledgeable might be able to lend a hand. I haven't done anything more complicated than basic addition, subtraction, multiplication etc. for a number of years, and most of the knowledge I did have when I was younger has since atrophied, unfortunately (to be replaced with far less useful information, I'd venture). My problem is as such: I have the following equation

and want to express x as a function of y and z. I have tried my darndest but don't seem to be able to do it, so what I'm wondering is (a) if it's even possible, and (b) how to get there, if so. Any assistance would be greatly appreciated.

Thanks in advance!

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Algebra q

Hi;

This answers a)

Welcome to the forum.

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In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Marquis de Saint-Loup

Guest

Re: Algebra q

Words cannot express my appreciation. It took me all day to even get to the point where I figured out I couldn't figure it out! (Still, I'd love to know what you did that I apparently missed, if you have the time and inclination to humour me.)

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Algebra q

Hi;

Words cannot express my appreciation.

You do not need to express it. I did not do very much.

(Still, I'd love to know what you did that I apparently missed, if you have the time and inclination to humour me.)

I would love to demonstrate something brilliant here but as of yet it is not coming to me. Remember I said in post #2 that I was only answering a). Proving that it was possible.

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Bob

Administrator

Registered: 2010-06-20

Posts: 10,583

Re: Algebra q

hi,

Isn't it just the quadratic formula with a bit of algebraic manipulation thrown in.

Bob

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Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Algebra q

Hi Bob;

Yes, I agree.

Hi Marquis de Saint-Loup;

Your equation can be arranged to:

Now use the quadratic formula:

with

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Marquis de Saint-Loup

Guest

Re: Algebra q

You do not need to express it. I did not do very much.

Well, as far as I'm concerned, you did! I'd managed to solve it for x using the quadratic formula once I plugged in specific values of y and z, but trying to get the generalisable solutions was like banging my head against a wall. Anyway, as simple as it may seem to you (and as simple as it looks now I understand what you did), I am nonetheless very grateful.

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Algebra q

Hi;

You are welcome.

was like banging my head against a wall

Without a hard head you can not do math. It is true that the human cranium softens with age so I wear a helmet.

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Marquis de Saint-Loup

Guest

Re: Algebra q

An ingenious solution. I also wear a helmet, but in my case it is to protect myself when I'm sitting at my desk; where most chairs have at least three legs and are thus stable, I could only afford a chair with one, so unless I am balanced perfectly it tends to tip over.
Perhaps there is a causal relationship between cranial firmness and mathematical ability... someone with a bit of business acumen might be able to make their fortune offering to improve students' test scores by replacing their heads with bricks and similar hard objects.

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Algebra q

where most chairs have at least three legs

An interesting hypothesis. I will have to check that.

I could only afford a chair with one, so unless I am balanced perfectly it tends to tip over.

You do sound like a well balanced individual to me. Could this be from your uni-legged chair? I have immediately sawed off 2 legs from my chair to duplicate yours.

by replacing their heads with bricks and similar hard objects.

So you got that idea too, bravo! The guys went for it right away. Soon I was out of bricks and had to use cinder blocks.

http://en.wikipedia.org/wiki/Concrete_masonry_unit

Alas, the gals would not go for it. They insisted that their sunglasses just did not look right on a brick.

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In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.