先化简再求值 x-2分之x-4+x²-4x+4分之4÷x-2分之x,其中x=根号2

(x-4)/(x-2)+[4/(x²-4x+4)]÷[x/(x-2)]=(x-4)/(x-2)+[4/(x-2)²]×[(x-2)/x]=(x-4)/(x-2)+4/x(x-2)=[x(x-4)+4]/[x(x-2)]=(x-2)²/[x(x-2)]=(x-2)/x x=√2,∴原式=(√2-2)/√2=1-√2