Statistics
2nd → MODE → run QuadReg from the catalog, which automatically detects lists L1 and L2 and saves the results to a temporary equation that cannot be stored to Y1 without reinstalling the OS.
STAT → EDIT → choose QuadFit option inside the edit menu, which will place the coefficients into the HOME screen, and then press TRACE to save to Y1.
STAT → CALC → QuadReg → set Xlist to L1 and Ylist to L2 → press VARS → YVARS → Function → Y1 to store, then ENTER to compute and save the equation to Y1.
VARS → STAT → QUAD → select AUTO store which sends the regression to Y3 by default and requires you to manually copy coefficients into Y1 afterward in the Y= editor; this is the recommended method.