Answer:Z(-5,14)
Step-by-step explanation:Here, X (3,4) is a coordinate. And Y (-1,9) is a midpoint.
Let another endpoint of line be z(x,y)
We have,
Midpoint of XZ=((x1+x2)/2,(y1+y2)/2)
that is, (-1,9)=((3+x)/2,(4+y)/2)
Equating with their corresponding elements we get,
-1=((3+x)/2
-2=3+x
∴x=-5
Now,
Equation with their corresponding elements, We get,
9=((4+y)/2)
18=4+y
∴y=14
∴The coordinates of z are (-5,14).