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70X1+70X2+70X3+...+70X35=     SA FIE PATRAT PERFECT



Răspuns :

70(1+2+3+..+35)=70(35x36/2)=70x630=44100=(2x5x3x7)la2=210la2
[tex]70+70*2+70*3+.......+70*35= \\ Dam~factor~comun~pe~70: \\ 70(1+2+3+...+35)= \\ 70* \frac{35(35+1)}{2} = \\ Se~simplifica~2~cu~70: \\ 35*35*36= \\ 35^2*6^2=(35*6)^2=p.p[/tex]