mk chỉ bt làm câu 3 thôi
a)đkxđ: x≠2 ; x≠-2
rút gọn :
A= 2+x/2-x - 4x^2/x^2-4 - 2-x/2+x
=2+x/2-x - 4x^2/(x-2).(x+2) -2-x/2+x
=-(2+x)/x-2 - 4x^2(x-2).(x+2) -2-x/2+x
=-(2+x).(2+x)/(x-2).(x+2)- 4x^2/(x-2).(x+2) -(2-x).(x-2)/(x-2).(x+2)
=-(4+4x+x^2)-4x^2-(-4+4x-x^2)/(x-2).(x+2)
=-4-4x-x^2-4x^2+4-4x+x^2/(x-2).(x+2)
=-4x^2-8x/(x-2).(x+2)
=-4x(x+2)/(x-2).(x+2)
=-4x/(x-2)
b, A=-3<=>-4x/(x-2)=3<=>-4x=3x-6<=>-4x-3x=-6<=>-7x=-6<=>x=6/7