先化简再求值：(a-1)/(a^2-4a+4)×(a^2 - 4)/(2a-2),其中a=-1

显示全部楼层 · 2012-6-18 09:45:40

原式=（a-1）/（a-2）2×（a2-4）/2（a-1）=（a+2）/2（a-2）当a=-1时，原式=-1/6...

千问 · 2012-6-18 09:45:40

a-1/a^2-4a+4 * a^2-4/2a-2 =a-1/a^2-4a+4(a^2-1)/2(a-1)=a-1/a^2-4a+4(a+1)(a-1)/2(a-1)=a-1/a^2-4a+2(a+1)=a-1/a^2-4a+2a+2=a-1/a^2-2a+2=a-1/a^2-2(a-1)=a-1/a^2-2(a-1)a^2/a^2=((a-...