Question

Expalin how inflation unemployment trade off is not possible in the long run.

Answer 1

According to Friedman such trade-off— negative sloping Phillips Curve—can exist in the short run at least, but not in the long run. In the short run, Phillips Curve may shift either in the upward or downward direction as the relationship between these two macroeconomic variables is not stable. On the other hand, in the long run, according to Friedman, no trade-off exists between inflation and unemployment.
Reference:
https://www.economicsdiscussion.net/inflation/trade-off-between-inflation-and-unemployment-the-phillips-curve/17424