Manuel Pellegrini's side were rarely troubled by the hosts and took the lead when Silva tucked in following a brilliant backheel by Edin Dzeko.
Substitute Aguero added a second in stoppage time when he poked in after his initial shot was saved by Tim Krul.Dzeko had a shot blocked by Krul, who also stopped Samir Nasri's drive.
That was the sum total of City's best chances during a match in which they did not have to be at their best and their keeper Joe Hart - preferred to summer recruit Willy Caballero - was rarely tested.
Pellegrini was confident enough to leave influential striker Aguero on the bench and for £32m signing Eliaquim Mangala to remain in Manchester.
City got on top of Newcastle from the whistle, with Yaya Toure, the often maligned Martin Demichelis and another newcomer Fernando first to the second ball in dangerous areas without over-exerting themselves.
In attack, Silva, who did not show his true form at the World Cup, was back to his brilliant best while Montenegro's Stevan Jovetic, frustrated by niggly injuries in his first season, was exceptional in his role as roving midfielder.
The 24-year-old played the role of quarterback in the opening moments, producing a delightful lofted pass for Dzeko who could only strike his effort at Krul, who read the situation.
The Netherlands keeper, who played a starring role in the World Cup quarter-finals, was also called into action soon after when he dived to his right to prevent Nasri's piledriver from bursting the net.
Match facts
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Newcastle have won just once in the last six seasons in their opening match
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Silva's last four goals for Man City have all come away from home
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Aguero has scored 18 and assisted six goals in his last 24 league appearances.
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No defending Premier League champions have ever lost their opening game of the following season
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Containment seemed to be the Magpies' primary focus, although £12m midfield signing Remy Cabella was a willing outlet on his debut. Against a potent City side that defensive tactic rarely bears fruit, and seven minutes before the break the final line of defence was breached.
On this occasion, Toure found Dzeko in the area with a long pass and he then took two Newcastle defenders out with a backheel for Silva to stroke home.
Pellegrini's side had gone into the match having beaten Newcastle in their previous nine league meetings.However, late in the game that run looked like it would come to an end when substitute striker Ayoze Perez, who replaced ineffective fellow newcomer Emmanuel Riviere, was found in the area.
He jinked inside and fired in a shot that took a vital deflection off Fernando to take it past the post.
That was the best of two good opportunities for the Magpies, with full-back Paul Dummett heading over earlier when Hart misjudged a delivery into the area.
Newcastle lacked a cutting edge but, with promising attacking midfielder Siem de Jong waiting in the wings, manager Alan Pardew stressed afterwards he was happy with his options.
Magpies fans probably wish they could afford someone like Aguero, who dealt the final blow after coming on late to calmly slot in City's second, after his initial angled strike was saved.
Tributes were paid to Newcastle fans John Alder and Liam Sweeney who died in the Malaysia Airlines tragedy
Alan Pardew (left) had yet to get the better of City counterpart Manuel Pellegrini coming into the match
Both sets of players and the St James' crowd pay tribute to Newcastle fans John Alder and Liam Sweeney before kick-off
David Silva also scored against Newcastle on the opening day of last season
World cup finalist Sergio Aguero - rested at the start of the match - showed his sharp instincts for the goal
