Comments on: Calculus Answer Fail

By: protection asset

protection asset — Wed, 04 Aug 2010 13:58:54 +0000

top secret formula?

By: tom

tom — Thu, 03 Jun 2010 03:16:29 +0000

your wrong, yes the integral of x is x^2/2

But if you want to see y as the variable as you did when you integrated y to y^2/2 you now longer will be able to integrate y’ since y’ implies y is a funktion and it got a variable it depends on.
If you look at y as the variable their wouldn’t be an understanding of what y’ means.

“An elite” and “cjl” are correct.

The way they solved it:

dy/dx = y*0.85
(1/y)dy/dx = 0.85
(1/y)dy = 0.85dx
ln|y| = 0.85x + A
y = B*e^(0,85x)

and IVP gives is 19 = B*e^0 -> 19 = B*1

and now we’re done

By: The Dawg

The Dawg — Thu, 25 Feb 2010 08:42:43 +0000

Actually i think u’ll find that virtually all areas in calculus have their basis in either differentiation or integration.
So you fail!

-Applied Mathematics major

By: steven

steven — Thu, 25 Feb 2010 08:12:27 +0000

I would consider this a win not a fail

By: Yarns

Yarns — Wed, 03 Feb 2010 00:03:51 +0000

Wrong y = (0.85/2)y^2 + c
c = 19
its an IVP problem
thats an initial value problem, the intergral of x is x^2/2

By: callie

callie — Thu, 26 Nov 2009 19:00:38 +0000

The biggest fail of all is that this is labeled “calculus answer fail” it is a differential equation… not a calculus topic at all, even though in some calculus classes they teach basic first order separable differential equations like this one here. Still though it is hilarious. I wonder if anyone in my diff-eq class gave an answer like this on an exam. I will feel pretty sorry for the world of engineering if somebody would seriously answer like this. I’d be scared shitless!

-Aerospace Engineering major

By: WIN@notmail.nom

WIN@notmail.nom — Wed, 25 Nov 2009 01:55:29 +0000

and to be onest you are sort of a math wiz gman. don’t worry about it I’m nerdy about lord of the rings and history.!.!.! =D

By: WIN@notmail.nom

WIN@notmail.nom — Wed, 25 Nov 2009 01:52:05 +0000

no that would count as a WIN.

By: Gman

Gman — Mon, 23 Nov 2009 14:07:48 +0000

No guys, if you just invert the corivative of the fifth power of x, you get
y = 900e.85x^3/2sqrt(47/sin(y))
then you reduce the fractorial to the eighth power of pi, giving you
y = 9108πx*43x – 11.8sin(sqrt(x))
and finally you uninstantiate the third matrix inside the vector sphere, then redefactorize the quadruplex, then redux the 4 to a 5 to get
y = 3.

Duh.

By: slythwolf

slythwolf — Sun, 15 Nov 2009 04:00:46 +0000

You are mistaken, sir. Bloody Stupid Johnson is the failiest engineer ever.

By: Snamb

Snamb — Fri, 13 Nov 2009 22:24:40 +0000

Relly great answer

By: Shannon

Shannon — Fri, 13 Nov 2009 19:12:56 +0000

That’s not calculus, it’s algebra. Easy algebra.

By: Ultimatefailer

Ultimatefailer — Fri, 13 Nov 2009 09:01:33 +0000

Looks like the same handwriting to me :s

By: Warrior

Warrior — Thu, 12 Nov 2009 22:32:06 +0000

I like swords.

By: 1234

1234 — Tue, 10 Nov 2009 14:27:49 +0000

Um, that’s a win… shoulda done that in my algebra class all those years ago. Just to piss off the teacher a little more.

By: trr

trr — Tue, 10 Nov 2009 01:39:15 +0000

That’s close, calculus == dental plaque.

By: cjl

cjl — Mon, 09 Nov 2009 10:14:58 +0000

That doesn’t satisfy the requirement – that would only work if the initial equation was y’=0.85x. y’=0.85y with y(0)=19 is solved by y=19*e^(0.85x), as posted above.

By: blurb

blurb — Sun, 08 Nov 2009 22:23:03 +0000

you could also try:
(0.85/1.85)*x^1.85 + 19

Numerics are nice

By: Ghandi

Ghandi — Sat, 07 Nov 2009 08:57:47 +0000

SemiFail. The answer has already been given above:
y(x)=19exp(0.85x)
Your notation is too complex since
exp(0.85x+ln(19)) = exp(0.85x).exp(ln(19)) = exp(0.85x).19
so why keep the ln(19) in the argument of exp?

By: Ghandi

Ghandi — Sat, 07 Nov 2009 08:52:53 +0000

Fail!

The answer is already given above:
y(x) = 19e0.85x

By: Erik

Erik — Fri, 06 Nov 2009 17:30:50 +0000

Oh I simply love pulling Laplace transformations! Fantastic when you are modelling dynamic systems! )

By: PeggyU

PeggyU — Thu, 05 Nov 2009 09:59:29 +0000

I second that.

By: Studioneko

Studioneko — Thu, 05 Nov 2009 09:06:38 +0000

The handwriting of the student is the same of the teacher’s!
This is a fake.

By: Aubrey

Aubrey — Thu, 05 Nov 2009 05:20:45 +0000

It’d also be great if the teacher wrote “FAIL” under it in red pen.

By: Skull

Skull — Wed, 04 Nov 2009 22:54:42 +0000

y’ is the first derivative of y, so if y=19e^(0.85t) then
d/dt*y=y’=16.15e^(0.85t)

By: stupidass

stupidass — Wed, 04 Nov 2009 10:17:56 +0000

not a WRONG solution, but an awkward form.

y(x) = exp(.85x + ln(19))
y(x) = exo(.85x) * exp(ln(19))
y(x) = exp(.85x) * 19
y(x) = 19*exp(.85x)

By: Dave

Dave — Wed, 04 Nov 2009 10:07:01 +0000

And y’ equals what?

By: euwhui34hwuh

euwhui34hwuh — Tue, 03 Nov 2009 15:53:39 +0000

neeeeerdd

By: McFreddiez

McFreddiez — Tue, 03 Nov 2009 01:48:58 +0000

one of my friends didn’t know how to do a problem on the finals, so he just drew a narwhal.

By: boris

boris — Mon, 02 Nov 2009 17:49:05 +0000

The example in wikipedia was added after the post here. And it is correct.

By: Skull

Skull — Mon, 02 Nov 2009 03:28:57 +0000

just a little remainder, it’s thanks to “math nerds” that the internet exists, and pretty much all electronic devices wouldn’t exist if it weren’t for math

By: pepper

pepper — Mon, 02 Nov 2009 02:11:46 +0000

y= who cares(2)
y(87.664)
y(x)34=I dont give a SH**
~Therefore, Y= there’s math nerds everywhere

By: An elite

An elite — Sun, 01 Nov 2009 21:37:39 +0000

It isn’t: it’s

y(x) = 19e0.85x

By: ilikeit

ilikeit — Sun, 01 Nov 2009 19:10:25 +0000

hahhahahahaha that’s hilarious

By: Somepartsareme

Somepartsareme — Sun, 01 Nov 2009 16:24:06 +0000

*insta-win stamp*

And, Ryannon, usually I find you funny. But the assumption that anyone who can solve a complicated math problem never had fun as a kid is a little… ignorant.

By: britknee

britknee — Sun, 01 Nov 2009 09:18:21 +0000

who gives a shit what the answer really is?

By: Robert

Robert — Sun, 01 Nov 2009 03:45:32 +0000

Joe O is correct, Harrison has got what the function and what the free variable are… y is the function, there is no f(y)

By: uberfailz

uberfailz — Sun, 01 Nov 2009 00:39:14 +0000

Marker WIN!

By: jjmblue7

jjmblue7 — Sat, 31 Oct 2009 07:22:12 +0000

Baseball is fun? Since when?

By: Skull

Skull — Sat, 31 Oct 2009 04:32:11 +0000

one of the few things the french did right XD

anyway, here’s the solution using Laplace:

y’=0.85y
y’-0.85y=0
y(s)*(s-0.85)=y(0)
y(s)=19/(s-0.85)
y(t)=19e^(0.85t)

By: Bearycool

Bearycool — Sat, 31 Oct 2009 01:10:16 +0000

it is secret

By: Lucas

Lucas — Fri, 30 Oct 2009 14:45:53 +0000

And??? Lol, thats the answer….

If y(x) = 19exp(0.85x)

y’(x) = 19*0.85exp(0.85x)

or y’(x) = 0.85*19exp(0.85x)

or y’(x) = 0.85y(x)

and y(0) = 19exp(0.85*0), y(0) = 19*exp(0), y(0) = 19*1, y(0) = 19

Thats quite simple, I wish my Calculus tests were like this lol.

By: Pastor Zakilowskij

Pastor Zakilowskij — Fri, 30 Oct 2009 13:38:46 +0000

let’s just all stick to Wikipedia (like the teacher):
http://en.wikipedia.org/wiki/Initial_value_problem#Examples

By: Sabrina

Sabrina — Fri, 30 Oct 2009 05:17:17 +0000

Ghostbusters WIN

By: Selkceb

Selkceb — Fri, 30 Oct 2009 04:31:27 +0000

Whoops, forgot to plug in the 19.
y=19e^0.85x

By: Selkceb

Selkceb — Fri, 30 Oct 2009 04:19:04 +0000

Oh good, everyone else seems to agree with my answer.

By: Selkceb

Selkceb — Fri, 30 Oct 2009 04:09:40 +0000

y’=0.85y, y(0)=19
dy/dx=0.85y
dy/y=0.85dx
**//=>>intergrating symbol
//dy/y=//0.85dx
ln|y|=0.85x+C
y=e^(0.85x+C)
y=e^(0.85x)*e^C
y=(C_1)e^0.85x; C is a constant, ln|C| can be expressed as C_1 (still a constant)
y(0)=19
19=(C_1)e^(0.85*0), e^0=1
C_1=19
Im sure someone has already done this, but I’ve got nothing else to do (and I suspect I made a mistake).
Glad to see so many fellow engineering majors on this site.

By: arthur

arthur — Fri, 30 Oct 2009 03:36:01 +0000

It’ s the same letter!!

By: Oscar the Mild

Oscar the Mild — Fri, 30 Oct 2009 02:39:55 +0000

you have found the secret
!! – Beware teh Illuminati

By: watercoloredcat

watercoloredcat — Fri, 30 Oct 2009 00:39:23 +0000

And the truth is that I sound WAAAAAYYYYYYYYY smarter than I really am.