Would the flu go away if everyone that had it was quarantined at same time?

In theory, yes, the flu could be eradicated if everyone infected with the virus was isolated at the same time. This is because the flu is spread through contact with respiratory droplets from an infected person, so if there are no infected people to spread the virus, the outbreak will eventually die out. However, it would be extremely difficult to achieve perfect isolation of all infected individuals. Even if 99% of infected people were isolated, the remaining 1% could still spread the virus to others. Additionally, some people may be infected with the flu without showing any symptoms, so they would not be aware that they needed to isolate themselves. For these reasons, it is not realistic to expect that the flu could be completely eradicated through isolation alone. However, isolation can be an important tool for slowing the spread of the flu and reducing the number of people who become sick.