Question: `x^2 + 1/x^2 = 18` হলে `(x + 1/x)` = কত?
A
B
C
D
`sqrt(5)`
B
`2sqrt(5)`
C
`3sqrt(5)`
D
`4sqrt(5)`
Note: `x^2 + 1/x^2 = 18`
বা, `(x + 1/x)^2 - 2.x.1/x = 18`
বা, `(x + 1/x)^2 = 18 + 2`
বা, `(x + 1/x)^2 = (2sqrt(5))`
:.` x + 1/x = 2sqrt(5)`