27. 交换二次积分的次序：(1) \int _{\ 1}^{2}\text{d}x\int _{x}^{x^{2}}f(x, y)\text{d}y+\int _{2}^{8}\text{d}x\int _{x}^{s}f(x,y)\text{d}y(2) \int _{\ 0}^{1}\text{d}y\int _{0}^{y}f(x, y)\text{d}x+\int _{1}^{2}\text{d}y\int _{0}^{2-y}f(x, y)\text{d}x