x^2+3x-18/x^2+6x除以(x^2+9-6x) =(x+6)(x-3)/x(x+6)×1/(x-3)²=1/x(x-3)=1/(x²-3x)a^2-16/a^2+2a-8除以(a-2)*a^2+4-4a/a-2=(a+4)(a-4)/(a+4)(a-2)×1/(a-2)²×(a-2)²/(a-2)=(a-4)/(a-2)²=...又是你，csdygfx,谢谢你哈请采纳一下，好吗？