Give an example of how decisions by the supreme court , under chief justice john marshall strengthened federal power.

One example was during the Marbury vs. Madison case in 1803 where the court declared that the Judiciary Act of 1789 was contradictory with the Constitution making it invalid.  This was because the Court had the authority to assert that an act of Congress to be annulled if it was revealed to conflict with the Constitution.

i honesty don't know, good luck tho dawg