七年级数学分式的基本性质,

(1)(a^2+4a+3)/(a^2+a-6)=[(a+1)(a+3)]/[(a+3)(a-2)]=(a+1)/(a-2)(2)(x^2+y^2-2xy-9)/(x^2+6x+9-y^2)=[(x-y)^2-9]/[(x+3)^2-y^2]=[(x-y+3)(x-y-3)]/[(x+3+y)(x+3-y)]=(x-y-3)/(x+y+3)(3)(x^2+x-6)/(x^4-13x^2+36)=[(x+3)(x-2)]/[(x^2-4)(x^2-9)]=[(x+3)(x-2)]/[(x+2)(x-2)(x+3)(x-3)]=1/[(x+2)(x-3)]