Question

A point $(a,b)$ is called a good point if both $a$ and $b$ are integers. Number of good points on the curve $xy$ $=$ $225$ are

• A. 20
• B. 18
• C. 16
• D. 14

Answer 1

Answer: (B)

18

The order pair $(x,y)$ satisfying $xy=225$ are $(1,225),(3,75)(5,45),(9,25),(15,15)$. Order can be changed in the first four pairs and both $x$ and $y$ can be negative also, so the no. of pairs $=2(2\times 4+1)=18$