Hi,
Here’s a link to the [https://topics-cdn.dell.com/pdf/inspiron-15-5578-2-in-1-laptop_service-manual_en-us.pdf|service manual] for the laptop, taken from this [https://www.dell.com/support/home/au/en/aubsd1/product-support/product/inspiron-15-5578-2-in-1-laptop/docs|webpage].
Scroll to p.79 to view the necessary pre-requisite steps and then the procedure to remove the display assembly and then the palm rest assembly. This will allow access to the hinges.