Question

求证 全体自然数集与全体整数集等势

Answer 1

{0,1,-1,2,-2,3,-3,4,-4,5,-5,6,-6,.}

{0,1,2,3,4,5,6,7,8,9,10,11,12,.}

即 f(x) = 2x-1 (x>0), -2x(xN