While we’ve looked at finding the line of intersection of two planes, finding the point (or line) of intersection of three planes is actually no more difficult, so some of the questions below involve finding points (or lines) of intersection of three planes. Try to visualize the situation, and you may find GeoGebra helpful in approaching some of these questions.
Note that some of these questions instruct you to use elementary row operations (so, a matrix-based approach). I’m happy for you to use any (non-calculator) approach you like to answer these.
Exercise 13I question 1bc, 4abd, 5b, 8