Answer:
In the first excerpt, the purpose is to justify, and in the second is to to inform.
Explanation:
The declaration of independence is structured starting with a feeling from the country: "In every stage of these Oppressions", and the constitution's preamble starts stating who were the authors: "We the People of the United States"
Then, the declaration states who the authors are: "the Representatives of the united States of America" while the preamble shows the reasons of the coming constitution
Finally, the declaration states its main purpose and the preamble also declares the purpose of the constitution.
The tone in the declaration is dramatic, and in the preamble it is a lot more sober.
