x+1/x=√5 হলে, x³+1/x³

x+1/x=√5 হলে, x³+1/x³

B 3√5

C 5

D 2√5

Solution

Correct Answer: Option D

x³+1/x³ =(x+1/x)³-3.x.1/x(x+1/x)
             =(√5)³-3×√5
             =5√5-3√5
             =2√5