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A polynomial function f(x) satisfies the condition `f(x)f(1/x)=f(x)+f(1/x)` for all `x inR`,`x!=0`. If f(3)=-26, then f(4)=A. `-35`B. `-63`C. 65D. none of these |
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Answer» Correct Answer - B We know that a polynomial function f(x) of degree n satisfying. `f(x)f((1)/(x))= f((1)/(x)) ` for all `x(ne0) in R`is of the form `f(x) = 1 pm x^(n) ` for all `x (ne 0) in R`. We are given that f(3) =- 26. `therefore f(x) = 1 - x^(n)" ".....(i)` `rArr f(3) = 1- 3^(n)` `rArr -26= 1-3^(n)" "[becausef (3) = - 26]` `rArr 3^(n) = 27 rArr 3^(n) = 3^(3) rArr n = 3` Substituting n = 3 in (i), we get `f(x) = 1-x^(3) rArr f(4) = 1-4^(3) = - 63` |
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