Heres a more detailed definition of the formulas parameters. To use a built-in formula select Design Equation. Go to the options tab and be sure to check the boxes to display the equation on the chart.
Heres the linear regression formula.
Then right-click on the chart choose Add Trendline from the drop-down menu and then check the box for Display-Equation-on-Chart. Eq. Select the linear trend line for the type. To use a built-in formula select Design Equation.