Question

The least integer that must be added to (9798 x 9792) to make it a perfect square is

• A. 9
• B. 8
• C. 7
• D. 6

Answer 1

The correct option is A 9

$9798\times 9792=(9792+6)\times 9792$
$=(9792{)}^2+6\times 9792$
$=(9792{)}^2+2\times 3\times 9792$
$\text{∴ Perfect square number}$ $={9792}^2+2\times 3\times 9792+(3{)}^2$
$\text{∴ Last integer to be added to make 9798× 9792 a perfect square =}$ $(3{)}^2=9$