Determine whether each of the following sets are subspaces of r3 under the operations of addition and scalar multiplication defined on r3. justify your answers
w1={(a1,a2,a3)∈r3: a1=3a2 and a3=−a2}

Need on this geometry question. explain how you did it.

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?

Proportions in triangles solve for x