Curve Fitting Remix
This resource shows how I would remix "Curve Fitting" from Phet interactive Simulations (https://goopenva.org/courses/curve-fitting/view)
The original resource allows you to us your mouse, drag data points and their error bars, and watch the best-fit polynomial curve update instantly. You choose the type of fit: linear, quadratic, cubic, or quartic.
This is a powerful resource that can be used to introduce lines and curves of best fit. I recommend collecting data such as students' foot size versus height or use the attached lesson from the Virginia Department of Education.