Tìm y: \[ \frac{1}{10 \times 11} + \frac{1}{11 \times 12} + \frac{1}{12 \times 13} + \cdots + \frac{1}{y \times (y+1)} = \frac{1}{15} \]
Tìm y
----- Nội dung ảnh -----
\[ \frac{1}{10 \times 11} + \frac{1}{11 \times 12} + \frac{1}{12 \times 13} + \cdots + \frac{1}{y \times (y+1)} = \frac{1}{15} \]
