\begin{aligned} A_{1} P & = a_{2} + λ / 2 \\ A_{2} P & = a_{2} + λ \\ A_{3} P & = a_{2} + 3 λ / 2 \\ . . . \\ r & = a_{2} + m λ / 2 \end{aligned}

${\begin{align*}A_1P &= a_2 +\lambda/2 \\ A_2P &= a_2 + \lambda \\ A_3P &= a_2 +3\lambda/2 \\ &... \\ r &= a_2 + m\lambda/2\end{align*}}$

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