x^n-(x-Δx)^n≈d(x^n)=nx^(n-1)dx≈nx^(n-1)Δx
所以(x-Δx)^n≈x^n-nx^(n-1)Δx
1000^0.1=(1024-24)^0.1≈1024^0.1-0.1*1024^(-0.9)*24=2-2.4/512=1.9953(注:2^10=1024)