Show that the equation to the plane containing the line `y/b+ z/c =1, x=0,` and parallel to the line `x/a -z/c=1, y=0is x/a-y/b -z/c+1=0,` and if 2d is the shortest, distance between given lines, prove that `(1)/(d ^(2)) = (1)/(a ^(2)) + (1)/(b ^(2)) + (1)/(c ^(2)).`