Question

If f(x+1/x)=x²+1/x², then the value of f(3/2) is:

a) 5/4

b) 4/5

c) 1/4

d) -1/4

Answer 1

Ans. C)

f ( x + 1/x ) = x ² + 1/x² = ( x + 1/x )² − 2 x *1/x = ( x + 1/x )² − 2

Let x + 1/x = z. Then we get,

f (z) = z² − 2

Hence putting 3/2 on the place of z we get

f (3/2) = (3/2)² − 2

f (3/2) = 9/4 − 2 = 1/4 Ans.