已知X=2√2+1,求分式(X^2-2X-9)/(X^2-11X-15)的值.由已知X=2√2+1移项,得X-1=2√2两边平方,得X^2-2X+1=8X^2=2X+7把上式代入下式的分子和分母,得(X^2-2X-9)/(X^2-11X-15)=(2X+7-2X-9)/(2X+7-11X-15)=-2/(-9X-8)=2/(9X...