Can anybody please solve it.question is related to logarithms, range?

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1 Answer
Apr 27, 2018

#0<=x<=1# and #x=4# are all solutions to this equation.

Explanation:

First note that by using the change of base formula

#log_9x=(log_3x)/(log_3"9")=(log_3x)/2#.

Therefore

#2log_9x=log_3x#, and

#log_3x=log_9x^2#.

So we can transform

#log_3(sqrt(x)+abs(sqrt(x)-1))=log_9(4sqrt(x)-3+4abs(sqrt(x)-1))#

to

#log_9(sqrt(x)+abs(sqrt(x)-1))^2=log_9(4sqrt(x)-3+4abs(sqrt(x)-1))#.

Since the logarithm is a function, if the logs are equal then their arguments are equal.

#(sqrt(x)+abs(sqrt(x)-1))^2=4sqrt(x)-3+4abs(sqrt(x)-1)#

Because of the absolute value expressions, there are two cases here - when #x>=1# and when #0<=x<1#.

When #x>=1# we can ignore the absolute value signs and write

#(2sqrt(x)-1)^2=4sqrt(x)-3+4(sqrt(x)-1)#

#4x-4sqrt(x)+1=8sqrt(x)-7#

#4x-12sqrt(x)+8=0#

#x-3sqrt(x)+2=0#

#(sqrt(x)-2)(sqrt(x)-1)=0#

#sqrt(x)=2# and #sqrt(x)=1# which means that #x=4#, and #x=1# are both solutions. In fact, if we plug these values for #x# back into the original equation, we can see that both of these values work.

For #x=1#

#log_3(sqrt(1)+abs(sqrt(1)-1))=log_9(4sqrt(1)-3+4abs(sqrt(1)-1))#

#log_3(1)=log_9(1)#

#0=0#.

For #x=4#

#log_3(sqrt(4)+abs(sqrt(4)-1))=log_9(4sqrt(4)-3+4abs(sqrt(4)-1))#

#log_3(3)=log_9(9)#

#1=1#.

Now for when #0<=x<1#, we can rewrite the equation as

#(sqrt(x)-sqrt(x)+1))^2=4sqrt(x)-3+4(-sqrt(x)+1)#

#1=1#

Because this is ALWAYS true, there are an infinite number of solutions between and including 0 and 1.