Elitmus
Exam
If x>=y and y>1 , what is the maximum value of log (base x) -(x/y) + log (base y)x^2/y?
option
a) -0.5
b) 0
c) 0.5
d) 1
Read Solution (Total 4)
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- log(base x){(x^1/2)/y}+log(base y){y2/x} that was the question
on solving this expression we will be having,
=1/2[log(base X){X}]-log(base X){Y}+2[log(base Y){Y}]-log(base Y){X} since [log(base y){y}]=1 simlilarly [log(base x){x}]=1
=1/2-log(base X){Y}+2-log(base Y){X}=3/2-[log(base X){Y}+log(base Y){x}]
[log(base X){Y}+log(base Y){x}] this part can be solved by using property AM>=GM
([log(base X){Y}+log(base Y){x}])/2>=([log(base X){Y}+log(base Y){x}])^1/2 SO
([log(base X){Y}+log(base Y){x}])>=2([log(base X){Y}+log(base Y){x}])^1/2 OR WE CAN SAY ([log(base X){Y}+log(base Y){x}])>=2 WHERE 2 is it's minimum value and other values are 3,4,5...so on but in quetion we were asked to get maximum value of that expression we will have to put ([log(base X){Y}+log(base Y){x}])=2 in the expression 3/2-[log(base X){Y}+log(base Y){x}]=3/2-2=2.5-2=0.5
if we put ([log(base X){Y}+log(base Y){x}])=3
the we will have value=3/2-3=2.5-3=-0.5 so the maximum value of the expression would be=0.5
- 11 years agoHelpfull: Yes(8) No(8)
- log(base x){(x^1/2)/y} + log(base y){(y^2)/x)
= 1/2[log(base X){X}]-log(base X){Y}+2[log(base Y){Y}]-log(base Y){X}
=1/2+2 [since log(base X){Y}= -log(base Y){X}]
=5/2 Ans..
- 11 years agoHelpfull: Yes(3) No(1)
- 0.5 is the ans
- 11 years agoHelpfull: Yes(1) No(0)
- question is z= log x ((x^0.5)/y) +log y (y^2/x)
take x=y, then Z= log x (X^-1/2) + log y (y) = -1/2 +1= 0.5 (Minimum value)
take x>y, let x=4 and y=2
then Z=log 2 ( 2/2) + log4 (4) = 0+ 1= 1 (Maximum value)
Hence maximum value = 1 - 10 years agoHelpfull: Yes(1) No(1)
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