Verified Solution • 2025–26 Session moderate

QJEEM24Ma3b0a: JEE Main 2024 Mathematics - Class 11 JEEM24Ma3b0a Solution: If , then is equal to ___________.

If (1α+1+1α+2+…..+1α+1012)−(12⋅1+14⋅3+16⋅5+……+12024⋅2023)=12024\left(\frac{1}{\alpha+1}+\frac{1}{\alpha+2}+\ldots . .+\frac{1}{\alpha+1012}\right)-\left(\frac{1}{2 \cdot 1}+\frac{1}{4 \cdot 3}+\frac{1}{6 \cdot 5}+\ldots \ldots+\frac{1}{2024 \cdot 2023}\right)=\frac{1}{2024} , then α\alpha is equal to ___________.

Step-by-Step Verified Solution

amp;1α+1+1α+2+…+1α+2012−amp;(12×21+14×3+…+12024⋅12023)=12024amp;∑r=1101212r(2r−1)=∑r=11012(12r−1−12r)amp;=(1−12)+(13−14)+…+(12023−12024)amp;=(1+13+15+….+12023)amp;−(12+14+16+…+12024)amp;=(1+13+…+12023)−12(1+12+13+…+11012)\begin{aligned}& \frac{1}{\alpha+1}+\frac{1}{\alpha+2}+\ldots+\frac{1}{\alpha+2012}- \\& \left(\frac{1}{2 \times 21}+\frac{1}{4 \times 3}+\ldots+\frac{1}{2024} \cdot \frac{1}{2023}\right)=\frac{1}{2024} \\& \quad \sum_{r=1}^{1012} \frac{1}{2 r(2 r-1)}=\sum_{r=1}^{1012}\left(\frac{1}{2 r-1}-\frac{1}{2 r}\right) \\& \quad=\left(1-\frac{1}{2}\right)+\left(\frac{1}{3}-\frac{1}{4}\right)+\ldots+\left(\frac{1}{2023}-\frac{1}{2024}\right) \\& \quad=\left(1+\frac{1}{3}+\frac{1}{5}+\ldots .+\frac{1}{2023}\right) \\& \quad-\left(\frac{1}{2}+\frac{1}{4}+\frac{1}{6}+\ldots+\frac{1}{2024}\right) \\& \quad=\left(1+\frac{1}{3}+\ldots+\frac{1}{2023}\right)-\frac{1}{2}\left(1+\frac{1}{2}+\frac{1}{3}+\ldots+\frac{1}{1012}\right)\end{aligned}

amp;=(1+12+13+…+12023)−12(1+12+…+11011)amp;−12(1+12+…+11012)amp;=11012+11013+…+12023−12024amp;⇒α+1012=2023amp;⇒α=1011\begin{aligned}& =\left(1+\frac{1}{2}+\frac{1}{3}+\ldots+\frac{1}{2023}\right)-\frac{1}{2}\left(1+\frac{1}{2}+\ldots+\frac{1}{1011}\right) \\& \frac{-1}{2}\left(1+\frac{1}{2}+\ldots+\frac{1}{1012}\right) \\& =\frac{1}{1012}+\frac{1}{1013}+\ldots+\frac{1}{2023}-\frac{1}{2024} \\& \Rightarrow \alpha+1012=2023 \\& \Rightarrow \alpha=1011\end{aligned}

Related Learning Resources & Exam Preparation