How can you tell if your soultion is true for the system?

Me, the vertices of quadrilateral coat are c(2,0), o(7,0), a(7,2) and t(2,2). prove that coat is a rectangle.

Add the fractions and simplify 1/2+ 1/3

Which of the following would be a good name for the function that takes the weight of a box and returns the energy needed to lift it?