Points A = ( 3, 9) B = (1 , 1) c = ( 5, 3 ) and D = (a , b) lie in the first quadrant and are the vertices of quadrilateral ABCD. The quadrilateral formed by joining the midpoints of ab, bc, cd, and da is a square. What is the sum of the coordinates of point D?
I solved the problem but someone said that I could've solved it easier and faster by using vectors. I looked up vectors on google and I dont understand it that well. Could someone take a look at my work and show me where i could apply vectors.