The SUMX2MY2 function returns the sum of the difference of squares of corresponding values in two arrays. The "m" in the function name stands for "minus", as in "sum x2minus y2".
SUMX2MY2 takes two arguments, array_x and array_y. Array_x is the first range or array or range of numbers, and array_y is the second range or array of numbers. Both arguments can be provided as an array constant or as a range.