How do you verify the intermediate value theorem over the interval [5/2,4], and find the c that is guaranteed by the theorem such that f(c)=6 where f(x)=(x^2+x)/(x-1)?

1 Answer
Oct 20, 2016

Please see the verification in the explanation section.

Explanation:

f is continuous on [5/2,4]

Proof : f is a rational function and rational functions are continuous on their domains. f is continuous at all reals except 1. (Its domain is all reals except 1.) Since 1 is not is [5/2,4], f is continuous on that closed interval.

6 is between f(5/2) and #f(4)

Proof: f(5/2) = 35/6 < 36/6 = 6 and f(4) = 20/3 > 18/3 = 6

Therefore, there is a c in (5/2,4) with f(c) = 6

To find the c (or c's), solve the equation:

f(x) = 6.

Discard values outside (5/2,4).

Note the solutions are 2 and 3, but only 3 is in the interval.