The downloaded PDF might be called LP_3_ed.pdf. Rename it to Matemáticas_PreUC_Cap3_Funciones.pdf. This makes searching easy.
Many universities publish free official guides. Search for: libros preuniversitarios en pdf gratis install
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“Install” usually means saving the PDF and making it easily accessible on your phone, tablet, or computer. The downloaded PDF might be called LP_3_ed