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Differential Calculus

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1 Sep 2007 10:46:34 IST

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question on maxima and minima

None

find the value of a and b if y = alogx+bx²+x has its etreme values at x = -1 and x=2.

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Kanchan Avchare

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1 Sep 2007 10:47:08 IST

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need quick reply

tanmay gharat

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Joined: 24 May 2007

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1 Sep 2007 10:52:15 IST

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y'=o at x=-1 and x=2
hence,a/x+2*b*x^2+a=0 at these values of x
solving for a and b we get a=2 b=-0.5

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Joined: 5 Aug 2007

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1 Sep 2007 11:00:12 IST

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c extreme values r given

so y' will be equal 2 0
ther4
y' is cumin out 2 be
a + 2bx+1 = 0
x
put x = -1 , 2
x= -1
- a - 2b = - 1 ---------1

x=2
a/2 + 4b = -1 ----------2

solving d 2 eqs
v get
a = 2
b = - 1/2
plzz rate me

Krishna Gopal Singh

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Joined: 29 Dec 2006

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6 Sep 2007 21:39:31 IST

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Perfect answer rupali. And tango please check your differentiation

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Cool goIITian

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7 Sep 2007 20:11:16 IST

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Thanx very much sir

siva viper

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13 Sep 2007 01:52:08 IST

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but i thought log of negative value is not defined,am i wrong???????if not then how come u r all sayin taht it has extreme value at x=-1

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13 Sep 2007 10:22:03 IST

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basically u r right on ur part that log of -ve values r not defind

but here to find d maximum value v 1st hav 2 differentiate n then put d values

ther4 on diff. v dont get ny value containing log

i hope u got that point

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