I have also attached a QVF file with examples of each one so that you have something real to reference as you build these into your own applications. The below table shows the equivalent formulas in Qlik for the excel formulas provided. These excel formulas were sourced from Excel Tips From John Walkenbach: Chart Trendline Formulas

To make things as clear as possible I have included the Excel variants of these formulas so you have something to reference as I have done whilst checking these formulas calculate correctly. Here are some examples of exponential and 2nd order polynomial trend lines with the relationship expressed as a formula in the subtitle. I spent a little time working through the formulas required to mimic the trend lines that are available in QlikView and currently not available in Qlik Sense without knowing how to write reasonably complex expressions.