I want to reproduce this formula. Note The 1 in the F should be subindex

enter image description here

This is my MWE which is not working for me:

%!TEX TS-program = xelatex
%!TEX encoding = UTF-8 Unicode



            \item \textbf{F1}. Conocido como el F-Score, se le denomina en estadística a la medida de precisión de un test. Resulta de la combinación de dos valores: precisión y exhaustividad. F=\frac{Precisión \times Exhaustividad}{Precisión + Exhaustividad}

Additionaly, I don't know which format is better:

  • F in italic or not
  • · or x for multiplication
  • the formula after the text or centering below it

Packages related with formulas in my .cls file are:

  • 2
    Might be an idea to read a general introduction to LaTeX. For formulas you need math mode, you are not using math mode here.
    – daleif
    Commented Dec 12, 2016 at 12:34

1 Answer 1


\frac is only valid in math mode, so you want to either use inline math $ ... $ or displayed math for your equation. You make a subscript in math mode with an underscore, i.e. _{..}. Also, you want to use \text for the words in your fraction.

Inline math: $F_{1}=\frac{\text{Precisión} \times \text{Exhaustividad}}{\text{Precisión} + \text{Exhaustividad}}$

Or displayed math:
F_{1}=\frac{\text{Precisión} \times \text{Exhaustividad}}{\text{Precisión} + \text{Exhaustividad}}


enter image description here

  • The 2 should be multiplied here.
    – Academic
    Commented Sep 3, 2021 at 8:21

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