DETROIT — General Motors will make a $1 billion investment in its factories that will create or keep around 1,500 jobs. The investment is part of the normal process of equipping factories to build new models, and it’s been planned for months, a person briefed on the matter told The Associated Press this week.adcelannotate = {"mobilepaywallcategory" : "MOBILE_PREM-BUSINESS","nativepaywallcategory" : "NATIVE_PREM-BUSINESS"};