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Saturday, May 1, 2021

2021/028) Find non -ve integer x and y satisfying x^3 = y^3 + 2y + 1

We have y^3 + 2y + 1 > y^3

Further (y+2)^3 = y^3 + 6y^2 + 12y + 8 > y^3 + 2y + 1 

So we have (y+2)^3 > x^3 > y^3

So x^3 = (y+1)^3 = y^3 + 3y^2 + 3y +1 = y^3 + 2y + 1

Or 3y^2 + 3y + 1 = 2y + 1

Or 3y^2 + y = 0

Or y = 0 as we are considering non -ve roots

So solution x=1, y = 0

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