Any doubts on bitcoin functioning

[sl3ax]

Why for verify a bitcoin transaction it needs to generate a particular hash with any amount of leading zeroes which require a great computational work adapted for generating a hash every about 10 minutes and then a transaction is verified every about 10 minutes. I can understand this for get some amount of Bitcoin money,but for verify the transaction, why waste CPU/GPU resources?
If anyone can explain me this, i would appreciate it. 

[Strider Hiryu]

To prevent 'double spending': where a person spends their bitcoin (and gets something in return), but then submits a new transaction spending the same bitcoin on something else (robbing the original person they sent bitcoin to).  The mining is to prevent the second transaction from replacing the first.  Since the chain of blocks containing the first transaction will be longer than the chain of blocks the attacker could generate (unless the attacker has more processing power than 51% of the network).  It's so what has been spent stays that way.

[Stephen Gornick]

Why for verify a bitcoin transaction it needs to generate a particular hash with any amount of leading zeroes which require a great computational work adapted for generating a hash every about 10 minutes and then a transaction is verified every about 10 minutes. I can understand this for get some amount of Bitcoin money,but for verify the transaction, why waste CPU/GPU resources?
If anyone can explain me this, i would appreciate it. 

Bitcoin's essence is a system of money that has no central authority. 

The only way to prevent any party from exerting control and prevent individuals from cheating is to make the authority be consensus of the network, where participation comes from the expenditure of work.

Of course, if there was an easier way to accomplish this goal in a manner that is more efficient such a suggestion would be welcomed.  To date, not a single suggestion of an alternative has been workable.

[sl3ax]

I understand. Thanks.