How do I find displacement and its magnitude from position data?

[tinhnho]

hi everyone

please check if i was wrong. And I don't know how to find dx and dx and its magnitude, anyone have any idea? thanks

here the question http://viethost4u.com/toan/physic1.GIF

and here is my answer http://viethost4u.com/toan/answer.GIF

 

[HallsofIvy]

In calculating OA, you established that the positive x-axis was east and the positive y-axis is north. That means that any movement to the west or south is negative.

 

[tinhnho]

i don't get it ,can you explain which one i did wrong ?thanks

 

[tinhnho]

i got dx= -181.6 dy= 72, you was right, i have change bx= -400 and cy -188

please check if i 'm wrong

http://viethost4u.com/toan/answer.GIF