Ex 5 5/4=5:4=1,25=1,250...0 (5 urmat de 2012 de0)
a1+a2+a3+...+a2014=2+5+0+...+0=7
Ex 11 x10=(2*10+1)/(3*10-1)=21/29
ex12 r=a4-a3=17-13=4
a2=13-4=9
a1=9-4=5
Ex13 Formula 1 an=a1+(n-1)*r
n=5 r=3
a5=2+4*3=14
Ex 14. aplici formula 1
n=8 r=5
a8=a1+7*5=70
a1=70-35=35
ex 9Aplici formula 1
n=6 , r=4
a6=a1+5*4=-13
a1=-20-13=-33
Ex 6 rescrii exercitiul
2^0+2^1+2^2+2^3+...+2^n=2^(n+1)-1 2^0=1
Etapa verificarii n=0
2^0=1 ;2^1-1=1
demonstratie Pn adevarata
Pn=1+2+2^2+2^3+...+2^n=2^(n+1)-1
P(n+1)=[1+2^2...+2^n]+2^(n+1)=2^(n+2)-1
Inlocuiesti paranteza dreapta cu echivalentul ei din prima relatie
2^(n+1)-1+2^(n+1)=2^(n+2)-1
2^(n+1)+2^(n+1)-1=2^(n+2)-1
