计算:(2011³-2×2011²-2009)/(2011³+2011²-2012)

问题描述:

计算:(2011³-2×2011²-2009)/(2011³+2011²-2012)

设2011=a,则原式:(a³-2a²-a+2)/(a³+a²-a-1)=(a²-1)*(a-2)/(a²-1)*(a+1)=a-2/a+1=2009/2012.不懂再问我我会说的详细点,