For \(a,x,y,z\) are positive real numbers satisfy \(xyz=1\) and \(a\ge 1\). Prove that \(\dfrac{x^a}{y+z}+\dfrac{y^a}{x+z}+\dfrac{z^a}{x+y}\ge\dfrac{3}{2}\)

-Like Nesbitt's inequality, i have a problem it's a general formula of Nesbitt's inequality, if necessary please inbox to me :)