分子分母都有理化：
原式=lim(x→-8)(1-x-9)/(√(1-x)+3)*(4-2x^(1/3)+x^(2/3))/(8+x)
=lim(x→-8)-(x+8)/(x+8)*(4-2x^(1/3)+x^(2/3))/(√(1-x)+3)
=-(4-2*(-2)+4)/(3+3)=2第二步看不懂，(4-2x^(1/3)+x^(2/3))/(8+x)是怎么来的？对分子有理化：√(1-x)-3=(√(1-x)-3)(√(1-x)+3)/(√(1-x)+3)=(1-x-9)/(√(1-x)+3)=(-x-8)/(√(1-x)+3)对分母有理化（用立方差公式）：1/(2+x^(1/3))=(2^2-2x^(1/3)+x^(2/3))/[(2+x^(1/3)(2^2-2x^(1/3)+x^(2/3)]=(2^2-2x^(1/3)+x^(2/3))/(2^3-x)=(4-2x^(1/3)+x^(2/3))/(8-x)