Mirip dengan yang sebelumnya… 4000=-2000??

Long ago, a clever mathematician used to cheat
people. Once he borrowed Rp.4000/- from a rich man.
After a few days, he borrowed Rp.2000/- from the
same man. Many days passed, the mathematician did
not return the money to the rich man. The rich man
went to the mathematician and asked to return the
money. But to his great surprise, the mathematician
replied that he had already paid the debt.

“See here, friend” said the mathematician “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 mathematician to prove that sum of 4000 and 2000
is zero, but not 6000. The Clever mathematician
agreed. He said:
Let a = 4000, b = 2000 and c = 6000

a + b =c
Multiply both sides by a + b

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

a*a + ab + ba + b*b = ca + cb

a*a + ab – ca = cb – b*b – ba

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

so

a = -b

= a + b =0

Hence by putting the values of “a” and “b” as 4000
and 2000 respectively, their sum is zero, so the
mathematician saw no need to pay any money to the
rich man. The above calculation has no doubt
surprised you as it did the judge??!!

now, if we put it in numbers:

(4000 + 2000) (4000 + 2000) = 6000 (4000 + 2000)

4000*4000 + 4000*2000 + 2000*4000 + 2000*2000 = 6000*2000 + 6000*4000

4000*4000 + 4000*2000 – 6000*4000 = 6000*2000 – 2000*4000 – 2000*2000

4000( 4000 + 2000 -6000) = -2000(-6000 + 4000 + 2000)

so

4000 = -2000