1. (x+2)/(x-1)=10
x+2=10(x-1)
x+2=10x-10
x+2-10x+10=0
-9x+12=0
x=12/9
2. sunt 6 cifre, numere distincte=> aranjamente de 6 luate cate 2 - 5(numere precum 01,02,03 ,04 05 nu se considera de 2 cifre).
[n!/(n-k)! ] -5 =(6!/4!) -5=5*6 -5 =30-5=25.
3.u= x1*i + y1*j, v=x2*i+y2*j => u*v=x1*x2+y1*y2=> u*v=2-1=1.