$A point (a, b) is called a good point if both \text{'} a \text{'} and \text{'} b \text{'} are integers. The number of good points on the curve x y=225 are$

$\text{ The order pair }(x,y)\text{ satisfying }xy=225\text{ are }(1,225),(3,75),(5,45),(9,25)\text{ and }(15,15)$

and order can be changed for first four pairs and both and can be negative also. The required pairs $=5+5+4+4=18$