Q.

If f:R[0, ) is a function such that f(x-1)+f(x+1) = 3f(x)1, then the period f(x) is

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answer is 12.

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Detailed Solution

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f(x-1)+f(x+1) = 3f(x)1

putting x+2 in xf(x-1)+f(x+3) = 3f(x+2)2

From 1 and 2 

f(x-13)+2f(x+1)+f(x+3)=3f(x)+f(x+2)

=3 3f(x+1)= 3 f(x+1)

f(x-1)+f(x+3)=f(x+1)3Putting x+2 in eq - 3f(x+1)+f(x+5)= f(x+3)4Adding 3 and 4 we get f (x-1) = - f(x+5) now put x+1 for x, f(x+6)5

putting x+6 in plane of x in 5f(x+6) = - f(x+12)From eq 5 again , f(x) = - -f(x+12)=f(x+12)

Hence the period of f(x) is 12

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