PLEASE HELPP MEEE ASAP WITH THIS LINK

What are “like terms”? why can we only add like terms?

Find the greatest common factor of the followig monomials 21u^5v,3u^4v^6, and 3u^2v^5

Which statement explains how you could use coordinate geometry to prove the opposite sides of a quadrilateral are congruent? a. use the slope formula to prove the slopes of the opposite sides are the same. b. use the slope formula to prove the slopes of the opposite sides are opposite reciprocals. c. use the distance formula to prove the lengths of the opposite sides are the same. d. use the distance formula to prove the midpoints of the opposite sides are the same.