Hey!!!
Answer is....
diagonals of square bisect each other at right angles.
let diagonal be 2x
Using Pythagoras in a triangle enclosed by a side and 2 half diagonals...




side of a diagonal=2 sqrt50

cm......
HOPE IT HELPS YOU '_'
I think it is yz but I and not completely sure
Gradient =(y1-y2) / (x1-x2)
(-6-8)/(6-8)
:7
y:mx+c
8:7(8)+c
c:-48
y:7x-48