Scatter Plots vs. Excel Scatter plot. 1 Independant Variable, 1 Dependant Variable Date for X Axis.

I am a real estate appraiser.  I use Excel and Power Query extensively.   I am trying to understand Power BI, and what a simple task in Excel seems daunting in PowerBI. I measure market change via linear regression and include a third-order polynomial. 

My data includes the Sold Price (Power Query Currency) and the date (PowerQuery Simple Date).  Creating a bubble graph and adding a regression line with the Y-Value and a Slope Function is easy.  I cannot figure out how I can do this in Power BI.  I want to generate data-driven commentary with Power BI Smart Narrative I generated 5 Charts for 18 Months, 12 months, 9 Months, 6 Months and the last 3 Months in order to visually see how the trends at different points are made.  Your input is highly appreciated.