两道数学题目(有关于分式的计算)急!

分子=(x^3+y^3)-(x^2y+xy^2)
=(x+y)(x^2-xy+y^2)-xy(x+y)
=(x+y)(x^2-2xy+y^2)
=(x+y)(x-y)^2
分母=-(x^4-2x^2y^2+y^4)=-(x^2-y^2)^2
=-(x+y)^2(x-y)^2
所以原式=-1/(x+y)
=-1/(0.5+0.75)
=-4/5
分子=(x^3-x^2)-(x-1)
=x^2(x-1)-(x-1)
=(x-1)(x^2-1)
=(x-1)^2(x+1)
分母=(x-1)^2
所以原式=x+1=10^2008-1+1=10^2008