For Health Reasons People Should Limit Their Efforts, for Instance

For health reasons people should limit their efforts, for instance, during sports, in order not to exceed a certain heartbeat frequency. For years, the relationship between a person's recommended maximum heart rate and the person's age was described by the following formula: Recent research showed that this formula should be modified slightly. The new formula is as follows: A newspaper article stated: "A result of the new formula is that the recommended maximum number of heart beats per minute for young people decreases slightly and for old people it increases slightly." From which age onward does the recommended maximum heart rate increase as a result of the introduction of the new formula? Show your work.