Math help thx

by homiee • 20 Jan 2011, 02:23 • Journals
Lim h -> 0

(x+h)^3 - x^3/h


Pls help :( or ill fail exams
Comments
45
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Enigma 20 Jan 2011, 02:32
might have helped if you would of asked this at an other time than 2:23 am CET
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homiee 20 Jan 2011, 02:36
U replied so your awake. Why not help me!!
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Enigma 20 Jan 2011, 03:09
shit at maths + cant think now...
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Notorious 20 Jan 2011, 02:39
x^3
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homiee 20 Jan 2011, 02:44
?
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Notorious 20 Jan 2011, 02:49
read silent his comment, hes correct

(x+0)^3 - x^3/0 =
x^3 - endless

so if x is a random number, ur answer is - endless
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s1LENT 20 Jan 2011, 02:51
though its infinity , if x < 0
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Notorious 20 Jan 2011, 03:00
agree, but it says H differs to 0, not x

so x will be a real number imo
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s1LENT 20 Jan 2011, 03:29
yes, but a real number can also be negative :)
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s1LENT 20 Jan 2011, 02:47
-minus infinity, IF ( x>0)
-infinity IF ( x< 0 )

might be wrong, no time to think about it :D
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homiee 20 Jan 2011, 03:04
The answer is correct but the problem is i dont know how to get the steps to the answer right. Do you know?
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s1LENT 20 Jan 2011, 03:18
well my thoughts were: (x+h) ^3 becomes ALMOST x^3 , cause its ALMOST x+ 0 ^3

then u have a look at x^3/h : h becomes smaller and smaller , until it ALMOST reaches 0 , so the term x^3/ h becomes bigger and bigger.

( lets say x^3 is a normal number e.g. 12 . 12/12 = 1 ( h = 12 in this case )

12/6 = 2
12/3 = 4
12/ 1,5 = 8 and so on -> so if h becomes smaller and smaller , x^3/h becomes bigger and bigger !

all in all u have a look at the results which are : x^3 MINUS infinity = - infinity.

thats for x > 0

but if x is < 0 the second term ( x^3/h becomes smaller and smaller, because 3 is an uneven number ( for example -2^3 = -8 )

so the result for x<0 is x^3 MINUS MINUS ( = PLUS ) infinity = infinity
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CrimZon 20 Jan 2011, 03:19
how come u say endless instead of infinity? :p
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s1LENT 20 Jan 2011, 03:20
tbh i didnt know the right word , just a quick look in the dictionary :D but thx, will edit it
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CrimZon 20 Jan 2011, 03:21
will look so much smarter if u throw in infinity :)
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rize 20 Jan 2011, 08:17
only if h is positive :)
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hattivatti 20 Jan 2011, 02:49
Tried Wolfram Alpha?
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Quiki 20 Jan 2011, 02:52
wanted to do it in matlab... though to tired :( + forgot how to do it in there :D
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homiee 20 Jan 2011, 03:08
Nvm guys i know why now. Thx for the help
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im a tree 20 Jan 2011, 04:29
Not knowing a single limit question will make you fail exams???

I have 5 hours to learn and practice 12 weeks worth of calculus. Any suggestions?
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DeactSeareal 20 Jan 2011, 04:44
yep, come mirc #Da.Unbeatables pmme lets play
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Shuki 20 Jan 2011, 09:24
Go back in time and punch yourself in the face.
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im a tree 20 Jan 2011, 11:57
Oh shit, I genuinely wrote that on my whiteboard under a list titled "Sort life out plan" a few hours before reading this comment. Woah.
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loazis 20 Jan 2011, 10:37
Get naked, crawl into the shower, maneuver into fetal position and cry.

Cry.
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crook 20 Jan 2011, 17:17
Ha, I'm always in the same position!
Usually if I get to it 1 week before the exam or deadline, I can manage.

But 5 hours is a lost cause :)
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nicon 20 Jan 2011, 11:26
-&#8734;
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garin 20 Jan 2011, 11:41
shouldnt u be given smth like .. 2x^2 + 4x + 8 (example)

then u sub. in (x+h) for the x's + put it all over 'h'

then u simply expand the brackets and simply?
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b4lu 20 Jan 2011, 11:43
a²+b²=c²

u dont need to know more
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FoaMeA 20 Jan 2011, 12:25
If x is a real number and not infinite, then the answer is "-infinite".
The solution:
lim (x+a)^3 - x^3/a = x^3 - x^3/0 = x^3 - infinite = -infinite

If x is infinite, then you got an exception case: infinite - infinite. The solution to this case is the world wide web. :)

Haven't done limits for like 3 years now, still nice. :D
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Thomasz 20 Jan 2011, 13:08
makkie examen toch :p

ik had de gele versie
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homiee 22 May 2011, 00:24
had 9/20, fail :(
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Thomasz 22 May 2011, 13:54
Hah :D ik 12 :p en ziedet zitn vo de volgende reeks examens?
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homiee 22 May 2011, 15:44
haha tvalt nog mee :p behalve boekhoudn :x


keb eco al bijna af en tis al :p

gij?
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Thomasz 22 May 2011, 16:10
boekhouden sla ik over..

vo de rest van alle vakken wel al iets gdaan ma ng nie egt ver geraakt :/
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Cstm 20 Jan 2011, 19:26
omg so easy.. back then when maths was easy.. :((
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