I'm not even remotely close to understanding the first problem I dont understand how I can prove this at all. The 2nd problem I really just need help starting If anyone has any inputs at all it would be extremely helpful
The first one is just a matter of substitution and algebra, for example:
For the second one, you need to find a normal vector. If you label the points A, B, and C (it doesn't matter which is which):
where is the vector from A to B and is the vector from A to C. Then the equation of the plane is:
Post again in this thread if you're still having trouble.