how do I solve this?

Question

given the function f(x)=x+1/x, find its inverse f^-1(x)

Answer 1

y = x + 1/x

yx = x² + 1

0 = x² - yx + 1

x = [y ± √(y² - 4)] / 2

f^-1(x) = [x ± √(x² - 4)]