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Algebra Level 2

How many positive real numbers are there such that x x x = ( x x ) x { x }^{ x\sqrt { x } } = {( x\sqrt { x } ) }^{ x }

EDIT

Details and Assumptions - You can't raise 0 to the power 0. So, 0 is not a solution


The answer is 2.

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7 solutions

U Z
Oct 31, 2014

x x l o g x = 3 2 x l o g x x\sqrt{x}logx = \frac{3}{2}xlogx

x l o g x ( x 3 2 ) = 0 xlogx(\sqrt{x} - \frac{3}{2}) = 0

x x can't be zero , thus 2 solutions

Log(1) = 0. x can not be equal to 0. So two solutions . 1 and 9/4.

Niranjan Khanderia - 6 years, 7 months ago

Zero is not a solution as zero can't be raised to power zero. Also, l o g ( 1 ) = 0 log(1)=0
So, two solutions are 1 1 and 9 / 4 9/4 and not 9 / 4 9/4 and 0 0

Karthik Sharma - 6 years, 7 months ago

exactly the same!!

Asim Das - 6 years, 5 months ago
Sophie Crane
Nov 8, 2014

Expand the right-hand side to get

x x x = x x × x x x^{x\sqrt{x}}=x^{x}\times \sqrt{x}^{x}

We are told that x is not 0,

x x = x x x^{\sqrt{x}}=\sqrt{x}^{x}

Akshay Bhatia
Nov 1, 2014

First take log on both sides...then on squaring we get x^3=9x^2/4... We can easily do the question by plotting curves between y=x^3 and y=9x^2/4 hence we will get 3 points of intersection out of which zero is not in the domain . hence only two possible solutions

x x x = x x 3 / 2 x^{x*\sqrt{x}} =x^{x^{3/2}}
( x x ) x = ( x x x x / 2 ) = x ( 3 / 2 ) x (x*\sqrt{x})^{x}=(x^x*x^{x/2} ) = x^{(3/2)x}
x = 1 O R i d e x t o t h e s a m e b a s e . . . . . x 3 / 2 = ( 3 / 2 ) x x ( x 3 / 2 ) = 0...... i f x 0. \therefore ~x=1~~~OR~~~ idex~~ to ~the ~same~ base..... x^{3/2} = (3/2)x \\ ~~~~~~~~~\therefore ~~x(\sqrt{x} - 3/2)=0......if x \neq0.
x can not be equal to 0. 0 can not be raised to any power.
So two numbers are 1 and 9/4.
(Please note, I have made correction.)




what about "1"? it is also a +v e real number and satisfies the equation.

Arunsimha Reddy - 6 years, 7 months ago

Log in to reply

Thanks. You are right. I have made correction.

Niranjan Khanderia - 6 years, 7 months ago
Lalit Kumar
Nov 10, 2014

1 for log x 9/4 for( x^1/2)-3/2

Take log of both sides to reduce the equation to :

x * Sqrt(x) log(x)=(3/2) log(x)

Thus, x * Sqrt(x)=(3/2), which implies Square root of x= 3/2 .

This gives x=9/4 which is one possible solution and the other one is 1.

2 solutions .. because you can substitute the x by 1 or 0

not 0, but 4

Eric Escober - 6 years, 7 months ago

You can't raise 0 to the power 0.

Karthik Sharma - 6 years, 7 months ago

You get one solution as 9/4 and other as 1. 0^0 is indeterminate

Aadi Naik - 6 years, 7 months ago

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