Not a mastercam question, but....

[biss03]

A fellow employee asked me about this math equation brought to her by her son last night. I think I derived the correct answer (boy did this bring back memories), but thought I would present it to all on this forum. You guys are sooo good at answering all other questions I figured why not!!

Here is the problem:

8(20+y+x)

good luck and thanks,

josh

[Bullines]

Are you trying to derive x or y or something else?

[Bill]

I may be wrong because it's only been 20 years since algebra but here goes:

160+8x+8y

unless they had an = sign to figure a variable

So is it right or should I stick to programming?

[This message has been edited by Bill (edited 06-06-2001).]

[Bill]

Actually, I went to college originally to be a math teacher and I have thought about going back to finish my degree.

[Bullines]

Exactly, Bill. Hard to tell what we're solving for. If the goal is to derive x if 8(20+y+x)=0, the equation becomes 160+8x+8y=0. Then we could find y with respect to x in the following manner:

8y + 8x = -160

8y = -160 - 8x

y = (-160 - 8x)/8 <- unsimplified

Then subsitute the y we found back into the equation:

160 + 8y + 8x = 0

Which would become 160 + 8((-160 - 8x)/8) + 8x = 0 and then we could solve for x. The process would be similar if we're solving for y. If it's something else, then I have no clue based on what we know so far.

[This message has been edited by Bullines (edited 06-06-2001).]

[Bill]

My thoughts exactly.

[s0l0seven]

My $150 dollar calculator says "to few Arguments"

[Bullines]

Does your calculator have a symbolic solver feature?. My TI-85 can't solve symbolically But a copy of Maple, MathCAD or Mathmatica could

[s0l0seven]

This calculator can do it all; its just figuring out how to tell it to do something is the bitch about it.

(TI-89)

[Bullines]

True. TI's user's manuals for their calculators tend to be the size of novels

[Mark H]

Hmmmm... manuals... Mastercam...

Nope, wont go there.

[biss03]

That was all the information that was given for the problem on the work sheet. I also came up with 160+8y+8x. If you substitute numbers for the x and y, they equate the same. I had the same problem with my calculator. I'm actually starting to think it was a trick question. it seems to me that the original equation is simplified from the one we have come up with. But I have no real idea!!Its only been 7 years for me since algebra!

[Bullines]

What grade is your co-worker's son in or what kind of math class is this for?

[Guest]

8(20+y+x) is not exactly a problem. there must be more information, it has to equal something otherwise its just a statement like 1 + 1 = 2

you cannot set it equal to zero and solve for a variable as mentioned earlier because then the statement is undefined.

[This message has been edited by mbowling (edited 06-06-2001).]

[Bullines]

Sorry. I was shootin' for a generic treatment of this example. I set it to 0 as a "if this was the case". The problem doesn't have enough info.

[Guest]

i gotcha

btw, while we're on the subject, ever heard that 1 = 0

[Bullines]

Yup. A good example is:

a = b

a^2 = ab

a^2-b^2 = ab-b^2

(a + (a - = b(a -

a + b = b

2a = a

2 = 1

Kinda funny when ya think about it

I also sort of remember another proof of 1 = 0 from a university calculus class that uses integrals.

[Guest]

not bad...the one from calculus that i remember uses divergence of sequences and series

ln(1 + x) = x - x 2 / 2 + x 3 / 3 - x 4 / 4 + . . .

Plugging in x = 1:

ln 2 = 1 - 1 / 2 + 1 / 3 - 1 / 4 + 1 / 5 - 1 / 6 + . . .

2 * ln 2 = 2 - 1 + 2 / 3 - 1 / 2 + 2 / 5 - 1 / 3 + . . .

2 * ln 2 = (2 - 1) - 1 / 2 + (2 / 3 - 1 / 3) - 1 / 4 + (2 / 5 - 1 / 5) - . . .

2 * ln 2 = 1 - 1 / 2 + 1 / 3 - 1 / 4 + 1 / 5 - 1 / 6 + . . .

2 * ln 2 = ln 2

2 = 1

 

there is one with imaginary numbers also, too bad i cant program with imaginary numbers to make imaginary parts...never have any scrap

[This message has been edited by mbowling (edited 06-06-2001).]

[Bullines]

So in a way, this thread was Mastercam related

[Guest]

exactly

[Allan Brown]

A small error in the conditions required here Bullines. Let's not lose faith in the laws of mathematics!

(a + (a - = b(a -

a + b = b (where a <>

You can only divide both sides by (a- if (a-<>0. i.e. a condition of a<>b is necesssary - otherwise it blows up. a=b is exactly the case though.

[biss03]

It is 7th grade math class.

couldn't the answer be an ordered pair?

If you set 8(20+y+x) = 0

subtract 160 from both sides 160+8x+8y = 0

divide both by 8 8x+8y = -160

this would be the answer x+y = -20

any 2 numbers that add up to -20 would be the solution for x and y.

what do you think?

[Bullines]

I would've lost marks on that one for not thoroughly explaining. It's been a while since I've done any proofs

Biss03, yup. If it's set to 0. But is it supposed to be?

[cadcam]

Biss03 i see you trying to tell the little one at home the answer after this.

it should be a straihgt forward thoght but after this. son you need to read this thread i don't know any other way to tell you.

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[Guest]

bullines is right, an explanation is necessary. you can't set it equal to zero and solve for a VARIABLE. and any two numbers that add up to -20 would make the equation true if it is set to zero. but that could be an infinite series of numbers not an ordered pair. an ordered pair (5,-5)ie. is typically used as a cartesian coordinate.

probably need to know what chapter his math book is dealing with

 

next week: having fun with derivatives

[This message has been edited by mbowling (edited 06-06-2001).]