\documentclass[12pt,a4paper,oneside]{book}
\usepackage[utf8]{inputenc}
\usepackage[spanish]{babel}
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{graphicx} \usepackage[left=2.54cm,right=2.54cm,top=2.54cm,bottom=2.54cm]{geometry}