A clever Accountant used to cheat people. Once he borrowed Rs.4000/- from a rich man. After a few days, he borrowed Rs.2000/- from the same man. Many days passed, the Accountant did not return the money to the rich man. The rich man went to the Accountant and asked to return the money. But to his great surprise, the Accountant replied that there is no need to pay the debt. "See here, friend" said the Accountant "the sum of 4000 and 2000 is equal to zero, so I do not have any balance to pay". The rich man took the matter to the court. When the judge came to know this, he was astonished. He asked the Accountant to prove that sum of 4000 and 2000 is zero, and not 6000.

The Clever Accountant agreed. He said:

let a = 4000, b = 2000 and c = 6000

Therefore………. a + b = c

Multiplying both sides by a + b

(a + b) (a + b) = c (a + b)

a² + ab + ba + b² = ca + cb

a² + ab - ca = cb - b² - ba

Taking out 'a' and '-b' as common from Left hand and Right hand sides respectively,

a ( a + b - c) = -b (-c + b + a)

Rearranging

a ( a + b - c) = -b (a + b - c)

Cancelling out (a + b - c) from both sides

so.... a = -b

OR
a + b = 0

Substituting the corresponding values of 'a' and 'b', i.e. a = 4000, b = 2000,

Implies that

4000 + 2000 = 0

HENCE PROVED

So funny !!

nice one buddy