a) =3x+15)/(x-3).(x+3)+(1)/(x+3)-(2)/(x-3)

=(3x+15)/(x-3).(x+3)+(x-3)/(x+3).(x-3)-(2.(x+3)/(x-3).(x+3)

=3x+15+x-3-2x-6)/(x+3).(x-3)

=6+2x)/(x+3).(x-3)

=2)/(x-3)

Vậy A=2/x-3 với x =\ =| 3

b) A=1/2)(x=\ =| 3) 

=> 2/x-3=1/2

=>2/x-3-1/2=0

=>4/2.(x-3) -x-3/2.(x-3) 

=0

=>4 - x+3 =0

=> x=7(tmđk) 

Vậy x= 7 thì A = 1/2

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