Excel can solve for unknown variables, either for a single cell with Goal Seek or multiple cells with Solver.

Before LAMBDA was introduced to Excel, you'd need to know how to use VBA or macros to create your own function. However, today, Excel's LAMBDA tool lets you do this using familiar Excel language ...

How to Use VBA to Access the Equation of a Trend Line on Microsoft Excel. Trend lines are a type of regression analysis, which is a way to study the relationships between variables.