表达式22: "L" Subscript, 1 , Baseline equals StartFraction, StartNestedFraction, 1 NestedOver "m" Subscript, 1 , Baseline , EndNestedFraction "M" Subscript, 1 , Baseline plus "M" Subscript, 2 , Baseline plus "m" Subscript, 2 , Baseline "C" Subscript, 1 , Baseline Over StartNestedFraction, 1 NestedOver "m" Subscript, 1 , Baseline , EndNestedFraction plus "m" Subscript, 2 , Baseline , EndFractionL1=1m1M1+M2+m2C11m1+m2