diff --git a/quad9/electrodinamica/homework/hw3/main.tex b/quad9/electrodinamica/homework/hw3/main.tex
index e5acfa3..5928094 100644
--- a/quad9/electrodinamica/homework/hw3/main.tex
+++ b/quad9/electrodinamica/homework/hw3/main.tex
@@ -50,7 +50,7 @@
 \[ (\X + \Y) \cdot (\X + \Y) = (\X + \Y)_\nu (\X + \Y)^\nu = (X_\nu + Y_\nu) (X_\nu + Y_\nu) = \]
 \[ = \underbrace{X_\nu X^\nu}_{> 0} + X_\nu Y^\nu + X^\nu Y_\nu + \underbrace{Y_\nu X^\nu}_{> 0} > 2 X_\nu Y^\nu = 2 \X \cdot \Y. \]
 
-Ara ens agradaria veure que $\X \cdot \Y \leq 0$ sota la mètrica de Minkoswki per acabar la demostració.
+Ara ens agradaria veure que $\X \cdot \Y \geq 0$ sota la mètrica de Minkoswki per acabar la demostració.
 
 \[ \left.\begin{array}{r}
   X_\nu X^\nu > 0, \\