(1)9ab-ab^3=(2)a^3-12a=(3)化简(ab-b^2)除以a^2-b^2/a+b=(4)化简(1/a-2)-(4/a^2-4)=(5)若ab=1,则(1/a+1)+(1/b+1)=

Question

(1)9ab-ab^3= (2)a^3-12a=
(3)化简(ab-b^2)除以a^2-b^2/a+b=
(4)化简(1/a-2)-(4/a^2-4)=
(5)若ab=1,则(1/a+1)+(1/b+1)=

Answer 1

(1)9ab-ab^3=ab(9-b^2)=ab(3+b)(3-b)
(2)a^3-12a=a(a^2-12)(若是实数范围内可以再分）
(3)分子：ab-b^2=b*(a-b)
分母：(a+b)*(a-b)/(a+b)=a-b
相除得,答案为b
(4)(1/a-2)-(4/a^2-4)= (1/a-2)-(4/[(a-2)(a+2)])
通分算出答案为1/(a+2)
(5)把ab=1带入则(1/a+1)+(1/b+1)=(ab/a+1)+(ab/b+1)=a+b+2