2(2x-y-3z+2)+x+2y-z-6=05x-7z-2=0(1)同理消去z 得-x-7y+20=0(2)(1)(2)即x=-7y+20=(7/5)z+2/5x=(y-20/7)/(-1/7)=(z+2/7)/(5/7)即对称式方程为x/7=(y-20/7)/(-1)=(z+2/7)/5∴参数方程为x=7ty=-t+20/7z=5t-2/7
