[tex]\displaystyle \\
A= 1+2+3+...+458 = \frac{458(458+1)}{2}= \\ \\
= \frac{458\times 459)}{2}=229\times 459=\boxed{105111} \\ \\ \\
B=15+16+17+...+52 \\
\text{Daca sirul nu incepe de la 1, atunci se rezolva cu formula:} \\ \\
B = \frac{\text{(Nr. de termeni)(Ultimul termen + Primul termen)}}{2} \\ \\
\text{Calculam numarul de termeni: } \\ \\
n = 52 - 15 + 1 = 38 \text{ de termeni} \\ \\
B = \frac{38(52+15)}{2} = 19 \times 67 = \boxed{1273}
[/tex]