式40: "m" Subscript, 1 , Baseline "x" minus "m" Subscript, 1 , Baseline "S" Subscript, 1 , Baseline minus "m" Subscript, 1 , Baseline "R" plus "S" Subscript, 2 , Baseline equals "m" Subscript, 2 , Baseline "x" minus "m" Subscript, 2 , Baseline "S" Subscript, 1 , Baseline plus "m" Subscript, 2 , Baseline "R" plus "S" Subscript, 2 , Baselinem1x−m1S1−m1R+S2=m2x−m2S1+m2R+S2