Răspunsuri

2014-04-02T21:31:59+03:00
A1A60=A1A2+A2A3+A3A4+.................+A59A60
A1A60=1+2+3+..................+59=59x60/2=1770cm

A25A48=A25A26+A26A27+................+A47A48
A25A48=25+26+...............+47=72x11+36=828  (am grupat primul termen cu ultimul)
Era cu sume Gauss, nici nu mi-am dat seama Mersi mult :)
2014-04-02T21:37:14+03:00
A1A60=1+2+3+...+60=(60x61)/2=30x31
A25A48=A1A48-A1A25
A1A25=la fel ca sus=(25x26)/2=25x13
A1A48=la fel ca sus=(48x49)/2=24x49
=>A25A48=24x49 - 25x13  ......................faci tu calculele:)
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