Answer: These sources provided Shakespeare primarily with historical information. Moreover, Shakespeare borrowed ideas for the plot from them, and focused on some of the historical figures in his own work.
Step-by-step explanation:
Not all of Shakespeare's ideas are his own. Sometimes, Shakespeare found inspiration in other sources that he used. This is mainly true for his history plays - plays that are named after monarchs that ruled during a certain time period. Holinshed's Chronicles is believed to have been his primary source for history plays - Henry IV (part I and II), Henry V, Henry VI (all three parts), Henry VIII, Richard II, Richard III, but also for King Lear, Cymbeline and Macbeth. Shakespeare incorporated many Roman figures in his work, such as Julius Caesar, Antony, Cleopatra, etc. While doing so, he mainly relied on Plutarch's work, a text called Parallel Lives that consists of 40 biographies of Greek and Roman leaders.