Notice this is a geometric progression since each number multiplied by some factor equals the next number in the sequence, in this case,

Then by applying the formula for sum to infinity of a geometric progression,
Use slope formula: y2-y1/x2-x1
XZ: -5/9
YZ: 2/7
XY: -7/2
XYZ is a right triangle because two of these slopes have a product of -1.
(YZ and XY does). We are all busy these days.
Answer:
the answer is B hope this helps you