The shortest distance between the lines r¯=(2i¯−j¯−k¯)+λ(2i¯+j¯+2k¯) and r¯=(i¯+2j¯+k¯)+μ(i¯−j¯+k¯) is

a¯1=(2,−1,−1), a¯2=(1,2,1), b¯1=(2,1,2), b¯2=(1,−1,1), a¯1−a¯2=(1,−3,−2)numerator =[a¯1−a¯2   b¯1   b¯2]=9, b¯1×b¯2=3i¯+3k¯denominator=|b¯1×b¯2|=32s.d=numerator/denominator