Question

求(1/1-x)-(3/1-x三次方)的极限

Answer 1

x趋于1时,1/(1-x)-3/(1-x^3)=[(1+x+x^2)-3]/[1-x^2]=(x-1)(x+2)/[(1-x)(1+x+x^2)]=-(x+2)/(1+x+x^2)→-1(x→1).