`_____________P.Mui-mailove________________`

$$A = \left( \frac{1}{1+2} - 1 \right) \left( \frac{1}{1+2+3} - 1 \right) \dots \left( \frac{1}{1+2+\dots+2024} - 1 \right)$$$$\frac{1}{\frac{n(n+1)}{2}} - 1 = \frac{2}{n(n+1)} - \frac{n(n+1)}{n(n+1)} = \frac{2 - (n^2 + n)}{n(n+1)} = \frac{-(n-1)(n+2)}{n(n+1)}$$$$A = \underbrace{\left( \frac{-1 \cdot 4}{2 \cdot 3} \right) \cdot \left( \frac{-2 \cdot 5}{3 \cdot 4} \right) \cdot \left( \frac{-3 \cdot 6}{4 \cdot 5} \right) \dots \left( \frac{-2023 \cdot 2026}{2024 \cdot 2025} \right)}_{2023 \text{ thừa số}}$$$$A = - \frac{1 \cdot 2 \cdot 3 \dots 2023}{2 \cdot 3 \cdot 4 \dots 2024} \cdot \frac{4 \cdot 5 \cdot 6 \dots 2026}{3 \cdot 4 \cdot 5 \dots 2025}$$$$A = - \frac{1}{2024} \cdot \frac{2026}{3}$$$$A = - \frac{2026}{6072}$$$$A = -\frac{1013}{3036}$$

`\text \color{f#167}{--ARIS VANE--}`