Someone help-interesting math problem

[BLACK]

Extra credit math problem on my Calc test today. Couldn't fucking figure it out for the life of me. Looks so easy.


The sum of two numbers is 7 and their product is 25. Find the sum of their reciprocals.

I got this far:

x+y=7
xy=25
-------------------
x(7-x)=25
7x-x^2=25
-------------------------
Simple enough so far

0=x^2-7x+25
-----------------------

Doesn't factor; no problem

http://img265.imageshack.us/img265/5291/fuckingmathpt5.jpg

Anyone know what to do from here? D:

[Archaos]

I forgot what its called.
We did this shit in my math class either junior or senior year.
I think you multiply the top and bottom by the denominator of the opposite one.

if you get my drift.

so 7 minus the neg. squareroot of 51 times both the denom and numerator of the left side.

[BLACK]

Yeah, the answer is


7/25

[Talorth]

my answer is




+1!

[Digita1]

42.

[Archaos]

I so rule at math.

[BLACK]

Yeah, that was a pretty good call.

[damme]

You want to find the sum of their reciprocals, which is 1/x+1/y=(x+y)/(xy).
The rest is pretty simple, you have the two equations x+y=7 and x*y=25, so (x+y)/(xy)=7/25.

edit: Of course you "could" go on as you have done
2/(7+sqrt(-51))+2/(7-sqrt(-51))
= (2*(7-sqrt(-51))+2*(7+sqrt(-51)))/((7+sqrt(-51))*(7-sqrt(-51)))
= (2*7+2*7+2*-sqrt(-51)+2*sqrt(-51))/(7*7+7*sqrt(-51)-7*sqrt(-51)-sqrt(-51)*sqrt(-51))
= 28/(49+51)
= 28/100
= 7/25

But it's butt ugly and working with negative roots.. bleh.

[Bonk]

damme is the best :)

[HooB]

I can see that the LISP programming is going good damme ^^

[Archaos]

Whatever Damme. I beat you to the punch !

[Bonk]

hush pink shorts.

[BLACK]

TEST 04/04/07 TEST 95/100 A

FUCK YEAH, I didn't even need the extra credit.

[Archaos]

thats not 100/100...

I didn't teach you so that you could be a FAILURE !

j/k :P

[BLACK]

I know, that's what my parents said. I'm like. "MOM I GOT A 95!" "Why not a 100?"

[CharlieM]

You promised an interesting problem.
Come back when you are presented with a real life problem(presented in class :P) that you need to formulate your own complex algorithm (3d calculus) to solve it.

Thats interesting.

[BLACK]

I'm only a sophomore, 3d calc is wayyyyyyy later, lmao. I'm just in gimp ass AP. :/


Maybe interesting was the wrong way to describe it, but at the time it kicked my ass. Maybe I should have payed more attention in my Alg 2/Trig class last year.

[Archaos]

Math is gay anyway.

[Archaos]

You promised an interesting problem.
Come back when you are presented with a real life problem(presented in class :P) that you need to formulate your own complex algorithm (3d calculus) to solve it.


Whats that noise I hear?

Its the nerd alert.

[WiGgLr]

Whats that noise I hear?

Its the nerd alert.

It's been really loud since this post:

I forgot what its called.
We did this shit in my math class either junior or senior year.
I think you multiply the top and bottom by the denominator of the opposite one.

if you get my drift.

so 7 minus the neg. squareroot of 51 times both the denom and numerator of the left side.

[BLACK]

Taking Alg 2 in your senior year is not being a math nerd.


:P

[Pseudonymous]

Srry if you have trouble reading my hand writing, my b's look like 6's and my 7's might look like 2's and vise versahttp://img105.imageshack.us/img105/6789/mathproblemqv6.jpg

[Archaos]

Taking Alg 2 in your senior year is not being a math nerd.


:P

I alg 2 junior year.

ass.

[Pseudonymous]

i'm a sophomore in calculus :o

[Archaos]

you win life.

calc isn't even offered in my high school unless your a senior in advanced math.

[BLACK]

I'm a sophomore in AP calc. I r teh win. Doing nothing senior year ftw.

[Archaos]

I also did nothing senior year.

also freshman-junior years.

iowa educational system ftw

[CharlieM]

Algebra != calculus.

3d differential equations is where the fun is at.

[damme]

I'm taking abstract algebra this fall, that'll be some fun stuff. Took multidimensional calculus a few years back but forgot most of it and kinda need it now in the electromagnetism course I'm taking, mind helping me out getting started on a (simple) problem CharlieM?

[HooB]

You doing stuff in school damme ? That just can't be true :p

[damme]

I know, I must have brain cancer or something.

[CharlieM]

mind helping me out getting started on a (simple) problem CharlieM?

I dont lend myself to brain acrobatics unless absolutley necesarry.

[Pseudonymous]

you win life.

calc isn't even offered in my high school unless your a senior in advanced math.

Good thing i don't go to ur school<_<

[BLACK]

LOL @ doing homework on graph paper. LOL @ doing homework in general. :P

[Pseudonymous]

i do the majority on math on graph paper because that's all i have at my desk and my math binder is filled with graphing paper

[BLACK]

http://img454.imageshack.us/img454/2755/mafti1.jpg

[Archaos]

and?

[BLACK]

Find x imo.

[Zelaton]

I remember that shit from Senior year in High School. Jeez that was like 5 years ago. I suck at math now. :/

[BLACK]

I also suck at math. I'm more of an engrish person myself. I barely have an A in my math class while I could get a 20 on the engrish final and still have a 90.

[1095]

lol3844

[Zelaton]

I also suck at math. I'm more of an engrish person myself. I barely have an A in my math class while I could get a 20 on the engrish final and still have a 90.

Same, I'm more of an Art & English person. ^^

[Grog]

I FINISH ART IN TWO WEEKS YESSSSSSSSSSSSSSSSs

[Pseudonymous]

-.-http://i20.photobucket.com/albums/b212/necrofromhello/math_problem2.jpg

[damme]

(a+b)^p != a^p + b^p, Pseudonymous

[1095]

square, subtract, rinse and repeat

[Pseudonymous]

http://i20.photobucket.com/albums/b212/necrofromhell/math_problem3.jpg

[1095]

Distributive property doesn't apply to exponents.

[Archaos]

owned.

[damme]

You have to do it the way Descent said, Pseudonymous
sqrt(1+sqrt(2+sqrt(x)))=3 => 1+sqrt(2+sqrt(x))=9 <=>
sqrt(2+sqrt(x))=8 => 2+sqrt(x)=64 <=> sqrt(x)=62 =>
x=3844
Then check root to see if it's false. Which it's not.

[damme]

I think this fits here
http://pykus.com/images/Happy_Venn.png

[Damarus]

Theres a very small percentage when I'm happy while wearing pants. It's the time that the pants are still on, but they are about to be taken off.

[Tengil]

Theres a very small percentage when I'm happy while wearing pants. It's the time that the pants are still on, but they are about to be taken off.

You get happy when youre doing laundry? :???:

[Pseudonymous]

i asked my math teacher about the problem....the class tried to solve it but they ended up getting 2 different answers excluding mine and my math teacher had no fucking clue how to do it O_o

[1095]

r u serios?

[Pseudonymous]

unfortunately

[Archaos]

Wow. I sure hope that dude isn't teaching high school math.

[BLACK]

Holy shit, lmao.

[Pseudonymous]

Wow. I sure hope that dude isn't teaching high school math.

It's exactly what he's teaching xD

[Pseudonymous]

You have to do it the way Descent said, Pseudonymous
sqrt(1+sqrt(2+sqrt(x)))=3 => 1+sqrt(2+sqrt(x))=9 <=>
sqrt(2+sqrt(x))=8 => 2+sqrt(x)=64 <=> sqrt(x)=62 =>
x=3844
Then check root to see if it's false. Which it's not.

1 +(2^.25)+(3844^.125) = 4.995273378
.25 = 1/4 = quartic root
.125 = 1/8 = 8th root

i also plotted it on the graph and when x was 3844, it was 4.995273378, when it was .1867580934 y was equal to 3

o.o?

[BLACK]

D:

[damme]

Dude!
sqrt(1+sqrt(2+sqrt(x))) is NOT equal to 1+2^0.25+x^0.125

sqrt(1+sqrt(2+sqrt(3844))) = sqrt(1+sqrt(2+62)) = sqrt(1+sqrt(64)) =
sqrt(1+8 ) = sqrt(9) = 3

[Damarus]

Dude!
sqrt(1+sqrt(2+sqrt(x))) is NOT equal to 1+2^0.25+x^0.125/signed

[Pseudonymous]

oh, now i get it^^ whoops:)

[CharlieM]

Heres one I did 3 years ago in intro to 3d calculus.

Consider the problem of strapping a box down to the back of a truck.
The truck has a metal grid base with bars 30cm apart, to which straps can be easily attached. The box is 2m in one dimension, and has a fixed volume of 0.75m^3. Any length or width measurement of between 1.5 and 3m requires two straps placed 1m apart. Less than 1.5m requires only one strap.

Assume the box is placed in the truck with the 2m length longways.

Find the length of strapping required in terms of the width of the box. Graph the length of strapping over a suitable domain, and find the dimensions of the box (x, y and z) for the minimum ammount of strapping to be used.

http://home.iprimus.com.au/quarrion/images/box.jpg

[Talorth]

the answer is, 2!

[Archaos]

math is fucking gay

[Grog]

yeah!

[BLACK]

Cyeah Cyeah.

[CharlieM]

Go damme, answer my problem...GO!