Calculate the line integral of the vector field f = xy i + (x − y) j along c, the triangle composed of three segments. c1 is the line segment from (4, 0) to (-4, 0). c2 is the line segment from (-4, 0) to (0, 4). c3 is the line segment from (0, 4) to (4, 0).

Thank you for posting your question here at brianly. I hope the answer will help you. Below is the solution:

or segment from (4,0) to (-4,0), y is always zero because straight segment. 
in that case x*y=x*0=0 
and x+y=x+0=x 
if you choose x=4-t where t goes from 0 to 8 you should get 
r(t)=0i+(4-t)j