12/(1+3x)(1-3x)+(3x+1)/1-3x=1-3x/1+3x
12/(1+3x)(1-3x)+(3x+1)^2/1-9x^2-(1-3x)^2/1-9x^2=0
12+9x^2+6x+1-1+6x-9x^2=0
12x+12=0
x=-1
希望没看错你给的题,下次加括号
12/(1+3x)(1-3x)+(3x+1)/1-3x=1-3x/1+3x
12/(1+3x)(1-3x)+(3x+1)^2/1-9x^2-(1-3x)^2/1-9x^2=0
12+9x^2+6x+1-1+6x-9x^2=0
12x+12=0
x=-1
希望没看错你给的题,下次加括号