-3的倒数是——

-3的倒数=1/(-3)=-1/3补充如果[a/(a+1)-a/(a-1)]÷[a/(a+2)-1/(a²+2a)]a=-1/2那么原式=a[(a-1)-(a+1)]/[(a+1)(a-1)]÷(a²-1)/(a²+2a)=-2a(a²+2a)/(a²-1)²=-2(-1/2)(1/2²-2*1/2)/(1/2²-1)²=(1/4-1)/(-3/4)²=-(3/4)(16/9)=-4/3如果[1/(x+3)-1/(3-x)]÷2/(x-3)x=√3-3那么原式=[1/(x+3)+1/(x-3)](x-3)/2={2x/[(x+3)(x-3)]}(x-3)/2=x/(x+3)=(√3-3)/[(√3-3)+3]=(√3-3)/√3=1-√3温馨提示分子、分母若是多项式，用括号确定分子、分母的界限。