ab互为相反数,则有a+b=0,
cd互为倒数,则c*d=1,
|x| =1/2 则 x=±1/2
x²-(a+b+cd)* x +(a+b)^2009+ (-cd)^2010
=1/4 -1*|x|+0+1
=5/4±1/2
=7/4 或 3/4