7. use an "element argument" (that is, the direct proof approach in set theory, where you use a particular but arbitrarily chosen element) to prove the following statements for any sets a and b: (a) a c b b"-ac (b) (a-b) u (b-a) u (a b) =aub

Which is the equation of an ellipse with directrices at x = ±4 and foci at (2, 0) and (−2, 0)?

1foot = 12 inches; 1 yard = 3 feet

The architect's side view drawing of a saltbox-style house shows a post that supports the roof ridge. the support post is 8 ft tall. the distance from the front of the house to the support post is less than the distance from the post to the back of the house. how far from the front of the house is the support post positioned?