13.求下列函数的定义域:(1)y=(x−1)0+2x+1y=(x-1)^{0}+\sqrt{\frac{2}{x+1}}y=(x−1)0+x+12;(2)y=2−x−x2x+1−1y=\frac{\sqrt{2-x-{x^2}}}{\sqrt{x+1}-1}y=x+1−12−x−x2.