Question

1+3+5+..........+99=
va rog sa imi si explicati!!!!!!

Answer 1

    
[tex]\displaystyle \text{Aflam numarul de termeni: } \\ \\ n= \frac{99-1}{2}+1 =\frac{98}{2}+1 =49+1=50 \\ Folosim formula: \\ S= \frac{(\text{Numarul de termeni}) \times (\text{Suma dintre primul si ultimul termen})}{2} \\ \\ 1+3+5+...+99= \frac{n(99+1)}{2}=\frac{50(100)}{2}=50 \times 50 = \boxed{50^2}=\boxed{2500}[/tex]