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Algebra

Scorching goIITian

 Joined: 18 Feb 2012 Post: 264
19 Apr 2012 23:33:34 IST
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10
652
logarithm fallacy???
Engineering Entrance , JEE Main , JEE Main & Advanced , Mathematics , Algebra

log(1+2+3)=log1+log2+log3..possible...does it happen lyk ds???

Blazing goIITian

Joined: 21 Mar 2012
Posts: 1457
19 Apr 2012 23:43:26 IST
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Yes it happenes in many cases so no wonder

Scorching goIITian

Joined: 18 Feb 2012
Posts: 264
20 Apr 2012 00:01:22 IST
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specify cases......(if u feel it happens)

Blazing goIITian

Joined: 2 Mar 2012
Posts: 308
20 Apr 2012 00:29:37 IST
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### log(tanA + tanB + tanC) = log(tanA) + log(tanB)  + log(tanC)

Blazing goIITian

Joined: 30 Aug 2011
Posts: 359
20 Apr 2012 06:54:49 IST
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yes, of course

Forum Expert
Joined: 23 Jan 2007
Posts: 7958
20 Apr 2012 13:02:19 IST
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log(a+b+c) = loga + logb + logc is possible when a+b+c=abc

Examples : (2 , 4 , 6/7) ; (3 , 4 , 7/11)

Generalization : (x , y , (x+y)/(xy-1))....for above expression to be valid you can pick any x & y keeping in mind all numbers in triplet are positive.

Hot goIITian

Joined: 24 Oct 2011
Posts: 124
20 Apr 2012 15:56:04 IST
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I agree with Bipin Dubey....Just abc=a+b+c, is req condition generally..( But Log should not become undefined for value of log a,b,c, or a+b+c):)

Scorching goIITian

Joined: 18 Feb 2012
Posts: 264
21 Apr 2012 17:36:00 IST
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i got this result from dis log(1+3x+2x^2)=log((2x+1)(x+1))

Scorching goIITian

Joined: 18 Mar 2010
Posts: 278
22 Apr 2012 07:55:18 IST
1 people liked this

@ronnie what u hav written is more or less like log(a) = log(a) it is nothing to do with the ques the ques u have asked is about

if a+b+c = abc then log(a+b+c)=log(abc)

provided the satisfy the domain criteria of the function log(x)....................

Scorching goIITian

Joined: 18 Feb 2012
Posts: 264
22 Apr 2012 13:37:38 IST
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are pagle,put d value of x=1 and log1=0..u wl undrstnd.....

Scorching goIITian

Joined: 18 Mar 2010
Posts: 278
22 Apr 2012 17:57:29 IST
1 people liked this

listen if u put x=1 in log(1+3x+2x^2)=log((2x+1)(x+1))

u get log(6)=log(6)

got it ..........happy

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