Răspunsuri

2014-08-24T21:30:31+03:00

abcd barat =1000a +100b +10c +d =(6a +2b +3c +d) +( 994a +98b + 7c ) =(6a+2b+3c+d)+ 7(142a + 14b +c)     ⇒   7 divide (6a +2b +3c +d)  si 7 divide 7(142a +14b +c)    ⇒  7divide abcd   (abcd este divizibil prin 7) 
4 4 4
2014-08-24T21:40:57+03:00
Abcd=1000a+100b+10c+d=142a*7+6a+14b*7+2b+c*7+3c+d=7(142a+14b+c)+6a+2b+3c+d
7| (6a+2b+3c+d)⇒ 6a+2b+3c+d= multiplu de 7⇒ abcd este multiplu de 7