Let the intersection of the straight line L and L 1 be A (1-t,-1+2t,-1-t), then the direction vector of L is OA = (1-t,-1+2t). If t=2/3 can be solved, the direction vector of L is (2/3,-1/3, -4/3), or it can be written as (2,-1, -4), so the equation of straight line L is X/2 = Y/(-65438+).