13. a)a-3-5-7-9-...-1999=2+4+6+8+....+1998
a-1-3-5-7-....-1999+1=2+4+6+8+...+1998
(a-1)-1-2-3-4-....-1999=0
(a-1)-1999 * 2000 /2=0
a-1=1999 * 1000
a-1=1999000
a=1999001
e)2*{3*3*33:3:[84:21+(1*0*3+3+3a)*2+1]}=1764 :98
2* {297:3:[4+(0+3+3a)*2+1]}=1764:98
2*{99:[ 4+6+6a+1]}=18
2*{99:[11+6a]}=18
99:(11+6a)=9
11+6a=11
6a=0=> a=0
14. a,b numerele
a+b=452
a:8 = x,r=6⇒a=8x+6 ⇒3a=24x+18
b:12= x,r=6⇒b=12x+6 ⇒2b=24x+12
Scadem:....................-
3a-2b=6
Am obtinut un sistem.
a+b=452⇒a=452-b
3(452-b)-2b=6
1356-3b-2b=6
-5b=-1350
b=270
a=452-270 = 182
15. a,b =numerele
a-b=659⇒a=659+b
a:b=8,r=15
a=8b+15
659+b=8b+15
7b=644
b=92
a=659+92= 751
