(1)设t=根号3x-1>=0t^2=3x-1x=1/3t^2 1/3y=5-1/3t^2-1/3 t=-1/3t^2 t 14/3对称轴t=3/2'.'t>=0.'.y=0t^2=1-2xx=1/2-1/2t^2y=1/2-1/2t^2 t=-1/2t^2 t 1/2对称轴t=1'.'t>=0.'.y