Explanation: \(a_{3}=\left(a_{2}-1\right)^{2} \Rightarrow 64=a_{2}-1 \Rightarrow a_{2}=9\). একইভাবে, \(a_{2}=\left(a_{1}-1\right)^{2} \Rightarrow 9=\left(a_{1}-1\right)^{2} \Rightarrow a_{1}=4\) or \(a_{1}=-2\). Since the terms are squares, \(a_{1}\) must be a positive integer, so \(a_{1}=4\).
