2la8x3la7):(2la5x3la4)=2la3x3la3=(2x3)la3=6la3
(13la13x13la7):(13la1ox13la4)=13la20:13la14=13la6
(9la3x6la4):(9la2x6la5)la4=9la3x6la4:(9la8x6la20) (asta cred ca nu l-ai scris ok sau nu am inteles eu......
2la1997-2la1996=
2la1996(2-1)=2la1996
2la1997x3la1998-2la1998x3la1997=
se da factor comun 2la1997x3la1997
2la1997x3la1997(1x3la1-2la1x1)=
(2x3)la1997x(3-2)=6la1997