But it was not all good news for the Catalans, who lost Lionel Messi to a hamstring injury midway through the first half.
It is the third time the four-time World Player of the Year has hurt his hamstring this season, and Barcelona have confirmed he will receive tests on Monday to determine how long he will be out for.
Despite the severity of the scoreline, this was not an easy night for Gerardo Martino's side, who were under pressure from their hosts in the first half, until Neymar broke the deadlock on 35 minutes.
Less than two minutes seconds later, Pedro doubled the lead to put Barca's minds at ease, and Fabregas rounded off the victory in the second half by netting a brace.
Jorge Molina scored a penalty in injury-time but it was scant consolation for Pepe Mel's side, who stay bottom of the league.
Barca coach Tata Martino said: "We played the game that Betis wanted to play in the first 30 minutes. They left a lot of space and their pressure forced us back," said Martino, who added that Betis "deserved a goal in the first half hour of the game."
"When Cesc scored the third goal the game was over. We played an intelligent match."
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