How did economic interests tie northerners to the slave holding system of the south?

The idea of manifest destiny simply stated it was america's destiny to expand from the atlantic ocean to the pacific. the word "destiny" implies an idea that it was within our rights as a nation to expand. in a paragraph of 125+ words, explain what could be wrong with that idea.

Which expression is equivalent to (fg)(5)

Identify a reason for the decline of the roman empire.