Final answer:
An author's purpose in writing about Barack Obama could vary, encompassing to inform, persuade, entertain, or explain, often focusing on his career, presidency, and policies.
Step-by-step explanation:
When an author writes about Barack Obama, the author's purpose could be to inform the reader about his life and career, to persuade the reader to view him in a certain light, to entertain with anecdotes from his experiences, or to explain his policies and their impact. If the context is a political event such as Obama's keynote address at the 2004 Democratic National Convention, the aim might be to illustrate his rhetorical skills and the energy he brought to the political scene. When considering his presidency, the author might focus on comparing domestic policies or elaborating on his legislative challenges and achievements, such as the American Recovery and Reinvestment Act or the Affordable Care Act, in order to inform or persuade about their significance and outcomes.