Originally Posted by

**nalo6451** Hi all. I have attached the question and worked solution. I understand the steps for finding the normal. First, find two vectors on the plane, then using the vectors P_{1}P_{2} x P_{1}P_{3} to find the normal. After the normal is found the Cartesian equation can be obtained. What I need some clarification on is whether or not the inverse of the normal vector is still correct. ?? In the worked solutions you can see the vector PQ x PR was used by the author, whereas when I did the question I used QP x QR. As a result, I obtained the inverse equation (35i, -170j, -180k). Is my answer still correct, or did I go wrong somewhere?

I should also add I know order matters when taking the cross product (reversing order reverses the result), though I'm not sure if that's my error or if my error is in some other step.