因为a b互为相反数,c d互为倒数
所以a+b=0,cd=1
x=(2a+2b)/2+cd-1/2|m|
=a+b+cd-1/2|m|
=0+1-1/2*2
=1-1
=0
x^2-1/4(1-3x/2)-1/3x(2-x/2)
=0^2-1/4*(1-0)-0*(2-0/2)
=-1/4