Let f(x)=x^4 - x - 1. Show that f(x)=0 has two real roots.
The Attempt at a Solution
x(x^3 - 1 - 1/x) = 0 which gives x=0 and x^3 - 1 - 1/x=0, x^2 - 1/x - 1/x^2=0, but WolframAlpha says x~~0.724492 and x~~-1.22074. I kept dividing by x it but couldn't come up with a sound result.