If 
= 4, then
= _____ .
A
B
C
D
I think the answer should be 0. Can anyone please explain... the solution cannot help me to understand
Ans 1:
Class : Class 9
x+1/x=4
So,(x+1/x)^2=4^2=16
x^2+2+1/x^2=16
Since (x-1/x)^2=x^2-2+1/x^2,
It will be=(x+1/x)^2-4=16-4=12
So, (x-1/x)=√12
Which is equal to √2×2×3
=2√3
Ans 2:
Class : Class 9
x+1/x=4
So,(x+1/x)^2=4^2=16
x^2+2+1/x^2=16
Since (x-1/x)^2=x^2-2+1/x^2,
It will be=(x+1/x)^2-4=16-4=12
So, (x-1/x)=√12
Which is equal to √2×2×3
=2√3