According to the Dell beep code list for Inspiron Laptops, 8 beeps is an LCD failure. If doesn't elaborate but that could be the actual LCD screen, the interconnecting cable or it could be a logic failure on the motherboard. Sorry, but I can't tell you how to determine which one, except to replace, for example, the LCD screen with a new/known good one. If that fixes it, then the screen is bad, if not the problem is in the motherboard.
The other option is to take it to a PC repair shop, maybe they can determine what component has failed.
I am not a Dell Employee
Dell forum member since 2002
Dell Inspiron 15 - 5577 Laptop
Home Built Desktop PC with ASUS ROG Z170, i7 6700K CPU
Windows 10 64 bit Pro and Windows 10 Insider Program Beta Versions. SSD drives. Cakewalk by BandLab and Studio One 4.1 Recordng Studio Software.