Question

[(a-2)/(a^2+2a)-(a-1)/(a^2+4a+4)]÷(a-4)/(a+2)

谁帮我做啊?

Answer 1

原式=(a-2)/(a^2+2a)-(a-1)/(a^2+4a+4)x(a+2)/(a-4)
=(a-2)/a(a+2)-(a-1)/(a^2+4a+4)x(a+2)/(a-4)
=(a+2)(a-2)/a(a+2)^2-[a(a-1)]/a(a+2)^2x(a+2)/(a-4)
=(a^2-4-a^2+a)/[a(a+2)^2]x(a+2)/(a-4)
=(a-4)/[a(a+2)^2]x(a+2)/(a-4)
=1/a(a+2)