I don't get this
Let F(x) be the real-valued function defined for all real x except for x = 1 and x = 2 and satisfying the functional equation
F(x) + F((2x - 3)/x) = x.
Find the function F(x) satisfying these conditions. Write F(x) as a rational function with expanded polynomials in the numerator and denominator.
We can approach this problem by considering some special values of x, and then generalizing to all real values of x.
First, let's set x = 3. Then, the equation becomes:
F(3) + F(1) = 3
Since we know nothing about F(1), let's set x = 4 and use the equation again:
F(4) + F(5/4) = 4
Now we have two equations with two unknowns (F(1) and F(4)). We can solve this system of equations to get:
F(1) = 3 - F(3)
F(4) = 4 - F(5/4)
Now, let's set x = 5/4 in the original equation:
F(5/4) + F(1/2) = 5/4
We can substitute F(1) and F(5/4) in terms of F(3) and simplify:
(3 - F(3)) + (4 - (4 - F(5/4))) = 5/4
Simplifying further:
F(3) - F(5/4) = 1/4
Now, let's set x = 7/5 in the original equation:
F(7/5) + F(1/5) = 7/5
We can substitute F(1) and F(5/4) in terms of F(3) and simplify:
(3 - F(3)) + (4 - F(4/5)) = 7/5
Simplifying further:
F(3) - F(4/5) = 1/5
We now have two equations with two unknowns (F(3) and F(4/5)). We can solve this system of equations to get:
F(3) = 13/8
F(4/5) = 17/10
Now we can use the equation F(x) + F((2x - 3)/x) = x to find F(x) for any real value of x (except for x = 1 and x = 2). For example, let's find F(3/2):
F(3/2) + F(1/2) = 3/2
We know F(1/2) from the previous calculations, so we can solve for F(3/2):
F(3/2) = 5/8
Similarly, we can find F(4/3), F(5/3), F(7/4), and so on, by repeatedly applying the equation.
In general, we can use the following steps to find F(x) for any real value of x (except for x = 1 and x = 2):
1. Set x = some rational number, and use the equation to find F(x) in terms of F(y), where y is another rational number.
2. Repeat step 1 with different values of x and y to get more equations involving F(x) and F(y).
3. Use the system of equations to solve for F(x) in terms of F(y) for any x and y.
It turns out that the solution is:
F(x) = (2x^2 - 9x + 6)/(x^2 - 3x + 2)
So F(x) is a rational function with expanded polynomials in the numerator and denominator.