先化简,再求值:2x-6x-2÷(5x-2-x-2),其中x=1

显示全部楼层 · 2013-2-13 18:57:52

(2x-6)/(x-2)÷(5/(x-2)-x-2)=(2x-6)/(x-2)÷((5-(x-2(x+2)))/(x-2))=(2x-6)/(x-2)÷(9-x^2)/(x-2)=(2x-6)/(x-2)*(x-2)/(9-x^2)=2(x-3)/(3-x)(3+x)=-2/(3+x)=-2/4=-1/2...

千问 · 2013-2-13 18:57:52

=2(x-3)/(x-2)÷[5/(x-2)-(x2-4)/(x-2)]=2(x-3)/(x-2)×(x-2)/[-(x+3)(x-3)]=-2/(x+3)当x=1时原式=-2/(1+3)=-1/2...