stolyar wrote:

Find an integer F.

(1) F = 1/F

(2) |F| = 1/F

St:1 F=1/F or F- 1/F =0

F^2- 1/F=0, Now F cannot be equal to 0

So F^2-1= 0 or F =+1 or -1

Not sufficient

St 2 |F|=1/F

Now LHS is mod value and hence always non-negative. Therefore \(|F|\geq{0}\) or \(1/F\geq{0}\)

Note that F cannot be equal to zero as otherwise the expression becomes undefined.

Therefore |F| >0 or 1/F >0 -----Thus F>0

Since F>0 So we have F= 1/F or F^2=1 and F =1 as F >0

Ans is B

C is Trap answer here

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