Question

va rog de la ex. 14.DAU COROANA,4 STELE + FOLLOW

Answer 1

Răspuns:

14. a=21,b=9,c=30

15. x=25

16. problema are 3 solutii

17.x∈{1,2,3,4,5,6,7,8,9,10,11,12,13,14}

   y∈{14,13,12,11,10,9,8,7,6,5,4,3,2,1}

18.

Explicație pas cu pas:

14. a+b=30 => b=30-a

     b+c=39=>c=39-b=39-(30-a)=9+a

     c+a=51=> 9 +a+ a=51

     2a+9=51

     2a=42

     a=21

     b=30-a=30-21=9

     c=9+a=9+21=30

Verificare: a+b=21+9=30

                 b+c=9+30=39

                 c+a=30+21=51

15. 2+4+6+...+48+x=1+3+5+7+...+49

    2(1+2+3+...+24)+x= 1+3+5+7+...+ (2 . 25-1)

    2 . $\frac{24 . 25}{2}$+ x= 25 . 25

   24 . 25+ x= 625

  x=625-600

  x=25

16.1+2+3+4+5+6=21

   6+7+8=21

   10+11=21

17.x+y=15

1+14=15, 2+13=15, 3+12=15, 4+11=15, 5+10=15, 6+9=15, 7+8=15, 8+7=15, 9+6=15, 10+5=15, 11+4=15, 12+3=15, 13+2=15, 14+1=15

x∈{1,2,3,4,5,6,7,8,9,10,11,12,13,14}

y∈{14,13,12,11,10,9,8,7,6,5,4,3,2,1}