(x^2一4)/(x^2十3x)*(x^2一9)/(x^2一4x十4)=1
[(x-2)(x+2)]/[x(x+3)]*[(x-3)(x+3) ]/(x-2)^2=1[(x+2)(x-3)]/[x(x-2)]=1x^2-x-6=x^2-2x x=6