# multiply two points and matrix

I want to multiply two points and matrix.I have trainPoints which is trained before the program.And I have testPoints which is occured while program is processing.And also I have homography which is Mat object (calculated with findHomography method).I want to check is it true?I want to calculate homography error.How can i multiply two points and homography?

Your question is not clear enough. You should reformulate it. Can you write it in using mathematical conventions?

I have two points.Train points are (x,y) and test points are (x',y').I want to muliply x

homography and yhomography.For a result ,I want to get x' and y'.