First you have to replace each F(x) or functions like that with y. Then you swap the x (in some of your functions n) with the y. Step number three is to solve for y.
10. y=2x^5 -1
x = 2y^5 - 1
x + 1 = 2y^5
(x + 1) / 2 = y^5
[ ( x + 1 ) / 2 ] ^1/5 = y or all of the answer in brackets underneath a with the number 5
You then replace the y that is all by itself with the f^-1(x) or n
11. y = ( -5n + 20 ) / 2
12. y = - (x/2)^1/3 do the same thing as before and put it under a radical with the number three with the negative on the outside
The focus is left of the vertex, so the parabola opens to the left. The vertex is halfway between the focus and directrix, so the directrix is the vertical line x = 2