First slide

Functions (XII)

Question

$If f (x) is a polynomical function such that f (x) \cdot f (1 / x) = f (x) + f (1 / x) and f (2) = 9 then the value of f (4) =$

Moderate

A

70
B

62
C

65
D

75

Solution

$\begin{array}{l} f (x) = x^{n} + 1 \\ \Rightarrow f (2) = 2^{n} + 1 \\ \Rightarrow 9 = 2^{n} + 1 \Rightarrow 2^{3} = 2^{n} \Rightarrow n = 3 \\ Clearly, f (x) = x^{3} + 1 \\ f (4) = (4)^{3} + 1 = 65 \end{array}$

Get Instant Solutions

When in doubt download our app. Now available Google Play Store- Doubts App

Recieve an sms with download link

Doubts App

OR

SCAN ME

Doubts App

Doubts App