Question

(1+2+3+....+2012)×( 1 supra 2012 - 1 supra 2012×2013)

Answer 1

1006 este răspunsul . Atașez rezolvarea . Succes !

Answer 2

Aplicam formula:
$1+2+3+..+n = \frac{n*(n+1)}{2}$
=>
$(1+2+3+....+2012)*( \frac{1 }{2012} - \frac{1 }{2012*2013} ) = \\ \\ = \frac{2012*2013}{2}*( \frac{1 }{2012} - \frac{1 }{2012*2013} )= \\ \\ \frac{2012*2013}{2*2012}-\frac{2012*2013}{2*2012*2013}= \frac{2013}{2}- \frac{1}{2}= \frac{2012}{2}= 1006$