Show how to use the Intermediate Value Theorem to show that the equation 6x1+x6=43\displaystyle \frac{{6}^{{x}}}{{{1}+{x}^{{6}}}}=\frac{{4}}{{3}} has a solution between 1 and 4.

Let f(x)=6x1+x6\displaystyle {f{{\left({x}\right)}}}=\frac{{6}^{{x}}}{{{1}+{x}^{{6}}}}. In order for the Intermediate Value Theorem to apply we must first check that f\displaystyle {f} is on the interval [1,4]\displaystyle {\left[{1},{4}\right]}. You should verify this and be able to explain why it is the case.

We check the value of f\displaystyle {f} at the left endpoint of the interval [1,4]\displaystyle {\left[{1},{4}\right]}:
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f\displaystyle {f}() = .

And we check the value of f\displaystyle {f} at the right endpoint of the interval [1,4]\displaystyle {\left[{1},{4}\right]}:
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f\displaystyle {f}() =   .

The Intermediate Value Theorem guarantees a solution to f(x)=43\displaystyle {f{{\left({x}\right)}}}=\frac{{4}}{{3}} in the interval (1,4)\displaystyle {\left({1},{4}\right)} because
f(\displaystyle {f{{(}}})\displaystyle {)}\le f(\displaystyle \le{f{{(}}})\displaystyle {)}.
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