The Intermediate Value Theorem states that over a closed interval [a,b] for line L, that there exists a value c in that interval such that f(c)=L. We know both functions require x>0, however this is not a closed interval. However, I went ahead on the problem anyway. I decided to solve for x.

beninar6u

beninar6u

Answered question

2022-09-27

The Intermediate Value Theorem states that over a closed interval [ a , b ] for line L, that there exists a value c in that interval such that f ( c ) = L.
We know both functions require x > 0, however this is not a closed interval.
However, I went ahead on the problem anyway. I decided to solve for x.
2 x = 10 x
x 2 x = 10
x 2 l o g 2 = l o g 10
x 2 = 1 l o g 2
x = 1 l o g 2
However, when graphing these two functions I found that they both met up at 2.236, which is not equal to x = 1 l o g 2
I am very new to Calculus and the Intermediate Value theorem and would appreciate a simple explanation. Thank you.

Answer & Explanation

Phoenix Owen

Phoenix Owen

Beginner2022-09-28Added 6 answers

You have an error in one of the steps it should be as follows:
x 2 x = 10 ln ( x 2 x ) = ln 10 ln x + x ln 2 = ln 10.
To use IVT, let f ( x ) = x 2 x 10, now argue that it is a continuous function for x > 0. After this find two positive real numbers a and b such that f ( a ) < 0 and f ( b ) > 0. Then by IVT you can claim that there must be some point c in the interval [ a , b ] where f takes the value 0. This would mean c 2 c = 10.
If you try a = 1, you get f ( 1 ) = 2 10 = 8 < 0, now try a value for b.
gebuiteldmz

gebuiteldmz

Beginner2022-09-29Added 1 answers

The difference f ( x ) = 2 x 10 x is continuous on ( 0 , ). As f ( 1 ) = 8 < 0 and f ( 10 ) = 1023 > 0, the IVT tells us that there exists at least one c [ 1 , 20 ] with f ( c ) = 0.

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