Kindly help for these simple multiple type questions

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moonnightingale

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Kindly tell me answer for these 2 questions

For second one the answer is 20 i think
what abt the first one
 

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for the first, think about superposition:
bk = ak + FT(1)

for ak = bk for all k, then the fourier transform of 1 must be all 0's. for ak != bk for all k, then the fourier transform of 1 must be non-zero for all k. for a0 = b0, then it must be zero for at least the first coefficient. for a0 != b0, then it must be non zero for at least the first coefficient.
 

So kindly tell me answer
and am i correct for second one

Is it 20 Hz
 

If you could come up with a guess for the second one, why not try the first. It really should be obvious at this point. what is the DFT of f[n] = 1? The DFT will match one of the four cases listed above.
 

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