Algebra-2

if x,y,z are positive then minimum value of

xlog2y-log3z+2ylog3z-logx+3zlogx-log2y

a)1 b)12 c)3 d)6

16 Answers

1
skygirl ·

1 [by instinct :P]

1
Optimus Prime ·

u are wrong sky girl

106
Asish Mahapatra ·

(d) 6 ??

1
Optimus Prime ·

hey are u guys goin to ask each option and when i say no , then the one remaining will be the answer

106
Asish Mahapatra ·

arey see .. i think 2y=3z=x then all the powers wud be zero...

so. it will be 1+2+3=6

1
Optimus Prime ·

no its not six

so options remaining are b and c

106
Asish Mahapatra ·

then its (c) for sure [3]

1
Optimus Prime ·

asish give the solution, i have got only the answers , but i dont have solution, so plz give the solution, even i ll show u my half solution

1
Optimus Prime ·

applying A.M≥G.M to equation

≥33x(log2y-log3z).(2y)(log3z-logx).(3z)(logx-log2y)

≥ 33elogx(log2y-log3z).elog2y(log3z-logx).elog3z(logx-log2y

≥33e0
=3

nishant bhaiya is this method valid and is this correct

1
voldy ·

hey ek Q.
is it (2y) power

or 2 (y) power ??[7]

106
Asish Mahapatra ·

i guess it is correct...

106
Asish Mahapatra ·

even i thot it is 2*y.... :(

1
Optimus Prime ·

it is (2y) raise to

11
rkrish ·

@amit...

you are absolutely correct (post #10)

@asish...

even what you were thinking was rite (post #6)
but...you made 1 mistake.
x=2y=3z : true
but...i suppose,in the next step you put x=y=z=1.So you got 1+2+3=6.Instead if you had put x=1,y=1/2,z=1/3 i.e. x=2y=3z=1 you wud have got the correct ans !!! (1+1+1=3)

11
rkrish ·

@asish...

I'm sorry....i didn't see post #13

106
Asish Mahapatra ·

but i dint put x=y=1 then how can
x=2y=3z ... i was just mentioning that the powers wud cancel... then it wud be x0 + 2*y0 + 3*z0 = 6..

in that ur making the mistake of (2y).... and i thot 2*(y)....

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