x2+y2+z2=2,x+y+z=2 হলে 2(xy+xy+zx) এর মান কত?
A
1
B
2
C
3
Correct Answer: 2
(x + y + z)2 = (x2 + y2 + z2) + 2(xy + y2 + zx) = 2(xy + y2 + zx) = (x + y + z)2 – (x2 + y2 + z2) = 22 - 2 = 4 - 2 = 2