cum se rezolva exercitiile utilizind factorul comul:
110+220+330+440+550=
5+10+15+20+25+30+35=
11001+22002+33003+44004+55005=


Răspuns :

110+220+330+440+550= 110  + 110*2 + 110*3 + 110*4 + 110*5 = 110*(1+2+3+4+5) = 110 * 15 =  1650


5+10+15+20+25+30+35= 5* (1 +2+3+4+5+6+7) = 5*28 = 140



1999*2000-1998*1999-2*1998 =

= 1999*(2000-1998) -2*1998 =

= 1999*2 -2*1998 =

=2 * (1999-1998)=2



11001+22002+33003+44004+55005= 11001 * (1+2+3+4+5) = 11001 *15=165015