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\(\left(x^3-\cfrac{1}{y^3}\right)\propto \left(x^3 +\cfrac{1}{y^3}\right)\)
বা, \(\left(x^3-\cfrac{1}{y^3}\right)=k \left(x^3 +\cfrac{1}{y^3}\right)\) \([ k\) অশূন্য ভেদ ধ্রূবক\(]\)
বা, \( x^3-\cfrac{1}{y^3}=k x^3 +\cfrac{k}{y^3}\)
বা, \( x^3-k x^3 =\cfrac{1}{y^3} +\cfrac{k}{y^3}\)
বা, \( x^3(1-k) =\cfrac{1}{y^3}(1 +k)\)
বা, \( x^3y^3 =\cfrac{(1 +k)}{(1-k)}\)
বা, \( (xy)^3 =\cfrac{(1 +k)}{(1-k)}\)
বা, \( xy =\sqrt[3]{\cfrac{(1 +k)}{(1-k)}}=\) ধ্রুবক [প্রমানিত]