Identify the four different ways by which the constitution may be formally changed

The four different ways by which the constitution may be formally changed included:
1. Proposal by convention of states which is ratified by state convention.
2. Proposal by convention of states which is ratified by state legislature.
3. Proposal by state congress which is ratified by state conventions and 
4. Proposal by state congress which is ratified by the state legislature.
The most common one that is always used is proposal by state congress which is ratified by the state legislature.
These four ways are the paths for constitution amendment.