这些系数构成的向量和直线平行。

And, these coefficients here correspond to a vector parallel to the line.

youdao

看到了吧，系数变为0了，当直线垂直于法向量的时候。

So, see, this coefficient becomes zero exactly when the line is perpendicular to the normal vector.

youdao

特殊情况下，如果最后t的系数恰好是0的话，实际上这是会发生的，当直线平行于或处于平面上。

And, the special case is if this coefficient of t turns out to be zero in the end, and that's actually going to happen, exactly when the line is either parallel or in the plane.

youdao