Find the sum of all solutions to the equation above.
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Awesome solution!
Another way I like to think about it/present it is x x = x x = x 2 3 , so either x = 1 or x = 2 3 .
very elegant
x x = x x x ln x = ln ( x x ) x ln x − ln x − ln x 1 / 2 = 0 x ln x − ln x − 2 1 ln x = 0 ( x − 1 − 2 1 ) ln x = 0 Hence, the solutions are: ln x = 0 ⇒ x = 1 or: x − 2 3 = 0 ⇒ x = 9 / 4 1 + 4 9 = 4 1 3
From observation, 1 is a solution, and 0 is not as 0 0 is indeterminate. We also have:
ln ( x x ) = ln ( x x )
x ln x = ln ( x 2 3 ) = 2 3 ln x
x = 2 3
x = 4 9
Therefore the sum of the solutions is 1 + 4 9 = 4 1 3 .
x x = x x e x l n x = e l n ( x x ) x l n x = 2 3 ⋅ l n x → x 1 = 1 x = 2 3 → x 2 = 9 4 x 1 + x 2 = 4 1 3
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First note that x = 0 is not a solution, since 0 ∗ 0 = 0 but 0 0 = 0 0 is indeterminate. So given that x = 0 , we can write this equation as
x 2 3 x x = 1 ⟹ x ( x − 2 3 ) = 1 .
Now since 1 y = 1 for any real y we have that x = 1 is a solution.
For x = 1 , 0 we must have that x − 2 3 = 0 ⟹ x = ( 2 3 ) 2 = 4 9 .
The sum of all possible solutions is thus 1 + 4 9 = 4 1 3 .