Arsenal began their Premier League title challenge by beating Nottingham Forest 2-1 on Saturday as Alexander Isak scored twice in Newcastle's 5-1 thrashing of Aston Villa.After finishing second to Manchester City last season, Arsenal have splashed over £200 million on new signings to try and claim their first title for 20 years.Declan Rice, Kai Havertz and Jurrien Timber all made their debuts at the Emirates and the Gunners should have had a far more convincing scoreline to show for their performance.Eddie Nketiah opened the scoring after some sublime skill by Gabriel Martinelli opened up the Forest defence.Bukayo Saka then curled into the top corner from outside the area, but the Gunners were guilty of not killing the game off.Forest had barely threatened until the introduction of Anthony Elanga and Taiwo Awoniyi.Former Manchester United winger Elanga marked his debut with a fine run and cross for Awoniyi to score in his fifth consecutive Premier League game eight minutes from time."We were super dominant," said Arsenal boss Mikel Arteta. "There's no question that we deserved to win the game."We have to be more ruthless and more critical of ourselves to be more pushy and kill the games."Victory ensured Arsenal did not lose any early ground on City, who began the defence of their title with a 3-0 win at Burnley on Friday. Newcastle debutants shine Newcastle finished fourth last season to qualify for the Champions League for the first time in 20 years and their rise under the control of the Saudi sovereign wealth fund shows no sign of stopping.Italian international Sandro Tonali enjoyed a dream debut as he fired the Magpies into the lead after just six minutes.Villa equalised almost immediately through one of their own