x-y=10 এবং x3-y3=1900 হলে xy= কত?
A
20
B
30
C
40
D
50
Correct Answer: 30
x - y= 10x3- y3= 1900xy= ? x3−y3=(x − y)3+3xy (x−y)1900=(10)3+3xy.101000+30xy=190030xy= 1900-1000xy=900/30xy=30