f ( x ) = x 5 + 1 , find the number of real values of x such that f ( x ) = f − 1 ( x ) .
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@Calvin Lin Sir please help! Latex signs are not clear here !!
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You need to put your equations in \ ( \ ) , and not /( /). I've edited the first 2 equations for your reference.
Nice solution ! Upvoted!
f ( x ) = f − 1 ( x ) can be solved by graphing. Where the graph of f ( x ) is known and its inverse function will be the reflection of f with y = x . without graphing we can realize that there is only one intersection with y = x and therefore with f − 1
This problem takes a few steps. First, find f^{-1}(x). To do so, take the equation y = x^5 + 1, switch y and x, then solve for y. Set that equation equal to the original one, and then solve for x. I put it into Wolfram Alpha once it got to that point, in all honesty. It turns out there is just 1 real solution.
This is not a proper solution. Can you solve this problem without using computational device?
Any one can use wolfram alpha..you haven't made any efforts to solve the problem.
May be draw a rough sketch of it... i mean GRAPH it..
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The no of solutions of the equation f ( x ) = f − 1 ( x ) should occur for the ordered pairs of type ( a , a ) algebrically which gives us the equation
( x 5 − x + 1 = 0 ) which can have at most 5 real roots or at least 1. (think why ). Geometrically it is the point where the three curves f ( x ) , f − 1 ( x ) and x=y do meet together. To check whether f(x) has 5 ,3 or 1 real root we proceed as: f ( x ) = x 5 − x + 1
d x d f ( x ) = 5 x 4 − 1 so , d x d f ( x ) = 0 at x = ± 5 1 / 4 1 but we check for both values of x , f(x)>0. before and after the value range of x ϵ ( − 5 1 / 4 1 , 5 1 / 4 1 ) it is monotonically increasing or decreasing and prior to the decreasing range there must be a root but for x > − 5 1 / 4 1 as we see it is always positive. Therefore it ends to have a singe root and further only a single solution for the equation.