(9-6x+x^2)/(x^2-16)/(x-3/4-x)*(x^2+4x+4)/(4-x^2)
=(3-x)^2/(x+4)(x-4)*(4-x)/(x-3)*(x+2)^2/(2+x)(2-x)
=〔(3-x)^2*(4-x)*(x+2)^2〕/〔(x+4)(x-4)*(x-3)*(2+x)(2-x)〕
=〔-(x-3)*(x+2)〕/〔(x+4)*(2-x)〕
=〔(x-3)*(x+2)〕/〔(x+4)*(x-2)〕
=(x^2-x-6)/(x^2+2x-8)