because the x value is not repeated twice as it is in {(-8, -2), (7, -2),(-9,2), (0,0) {(5,8), (9,7),(-3,-8),(5,-5)} {(7,-8), (7, - 7), (8,4),(1, -3)}
A beat is an interference pattern between two sounds of slightly different frequencies, perceived as a periodic variation in volume whose rate is the difference of the two frequencies. Frequency beat is equal to,
The reference frequency in our case would be 392Hz, and since there is the possibility of the upper and lower range for the amount of beats per second that the two possible frequencies are heard would be
Therefore the two possible frequencies the piano wire is vibrating at, would be 396Hz and 388Hz
If a jump lasts for 1.8 seconds this means that from the moment when the person leaves the ground till the person touches the ground again it takes 1.8 seconds. So, maximum height reached will be at half the time of the jump i.e., 0.9 seconds.