First@Solve[a (x^4)+b (x^3)+c (x^2)+d x+e==0,x]//TeXForm

Solve[a (x^4)+b (x^3)+c (x^2)+d x+e==0,x][[1,1,2]]

Solve[a (x^4)+b (x^3)+c (x^2)+d x+e==0,x][[1,1,2]]//Simplify

Solve[a (x^4)+b (x^3)+c (x^2)+d x+e==0,x][[1,1,2]] // FullSimplify