The function $\mathrm{f}\left(\mathrm{x}\right) = \mathrm{a}\left[\mathrm{x}+1\right] + \mathrm{b}\left[\mathrm{x}-1\right], \left(\mathrm{a} \ne 0, \mathrm{b}\ne 0\right)$ where [ x ] is the greatest integer function is continuous at x = 1 if