解(x²+8x-20)/(x²-4)÷(10+x)=(x+10)(x-2)/(x-2)(x+2)×1/(10+x)=(x+10)/(x+2)×1/(10+x)=1/(x+2)刚刚那道题应该是这样,不好意思b²/3a³×9a²/2b=(b²/2b)×(9a²/3a³)=(b/2)...