What does it mean to cause source biased? why can bias
take away the credibility of the source?

To cause a source to be biased means that it is influenced by your opinion or another factor that is not factual. Bias can take away from the credibility because it is not completely true, as a source should be.

 Shay's rebellion was important to highlight the problems with the Articles of Confederation because it showed the people and government how terrible the Articles couldn't handle a crisis. 

 Many of the poorer people had to take large loans to keep their farms functioning while they were off fighting in the revolution. When the war ended, they had no money to pay the creditors back, who began pressing for the money. 

I hope this helps.