x2 -3x +1 =0 হলে (x2 - 1/x2) এর মান -

A    5√3

B    3√5

C    4√5

D    6√5

Solution

Correct Answer: Option B

 

x^2-3x+1=0

বা, x^2-3x=-1

বা, x(x-3)=-1

বা, x-3=-1/x

বা, x+1/x=3

বা, (x+1/x)^2=3^2

বা, (x+1/x)^2=9

বা, (x-1/x)^2+4.x.1/x=9

বা, (x-1/x)^2=9-4

বা, (x-1/x)^2=5

বা, x-1/x=√5   এখন, x^2-1/x^2=(x+1/x) (x-1/x)

                  =3√5

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