Wednesday, July 25, 2012

If x = log[a]bc y = log[b]ca z = log[c]ab ptove that x+y+z+2 = xyz

x = log a (bc)  


y= log b
(ca)


z= log c (ab)


Prove that
:


x+ y + z + 2 = xyz


We will
start from left side:


x+ y + z + 2 = log a (bc) + log b
(ca) + log c (ab) + 2


We know that: log b (x) = log a (x) +
log a (b)


Let us the base 10 as
a:


==>  (log bc/ log a)+(log ca/log b) +(log ab)/
log c) + 2 


We know that log ab = log a + log
b


==> (log c + log b)/ log a +(log c + log a)/log b
+(log a + log b)/log c  + 2 .........(1)


Now let us
calculate xyz:


xyz= log a (bc)* log b (ac)* log c
(ab)


      = log bc/ log a * log ac / log b * log ab/ log
c


      =(log b + log c)(log a + log c)(log a + log b)/ log
a*logb*logc


=[ logb(loga)^2 + logb*logc*loga + logc(loga)^2
+ loga(logc)^2+ loga(logb)^2 + logc(logb)^2 + loga*logb*logc +
logb(logc)^2]/loga*logb*logc


= loga/logc + 1 + loga/logb +
logc/logb + logb/logc + logb/loga + 1 + logc/loga


=
(loga+logb)/logc + (loga+logc)/logb + (logb+logc)/loga + 2
.....(2)


Now we can see that (1) and (2) are
identical.


Then we conclude
that:


x+y+z+2 = xyz

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