Binding energy

Binding energy can be understood as energy given off when a nucleus is formed from nucleons . It can also be considered as energy need to break off the nucleus into its constituent nucleons. If A = B + C + 2 neutrons. You can start with all the nucleons you need for forming A . Now energy is released to make nucleus A which is BE (A) . Starting with the same nucleons you can also make B and C which is BE(B) + BE(C). Since BE on the right hand side is more than the BE on the left hand side , more energy is released in forming B and C from A . Hence the difference in the BE is the energy released.