分式的基本性质约分：(1)9-x^2/x^2+5x+6(2)9a^2(x+y)/3a(x+y)(3)a^(n+2)-a^2b^n/a^(2n+1)-ab^2n(4)-(x+y)(x-y)^2/(y+x)(y^2-x^2)(5)a^2+b^2-c^2+2ab/a^2-b^2-c^2-2bc

分式的基本性质约分：(1)9-x^2/x^2+5x+6(2)9a^2(x+y)/3a(x+y)(3)a^(n+2)-a^2b^n/a^(2n+1)-ab^2n(4)-(x+y)(x-y)^2/(y+x)(y^2-x^2)(5)a^2+b^2-c^2+2ab/a^2-b^2-c^2-2bc
分式的基本性质
约分：
(1)9-x^2/x^2+5x+6
(2)9a^2(x+y)/3a(x+y)
(3)a^(n+2)-a^2b^n/a^(2n+1)-ab^2n
(4)-(x+y)(x-y)^2/(y+x)(y^2-x^2)
(5)a^2+b^2-c^2+2ab/a^2-b^2-c^2-2bc

分式的基本性质约分：(1)9-x^2/x^2+5x+6(2)9a^2(x+y)/3a(x+y)(3)a^(n+2)-a^2b^n/a^(2n+1)-ab^2n(4)-(x+y)(x-y)^2/(y+x)(y^2-x^2)(5)a^2+b^2-c^2+2ab/a^2-b^2-c^2-2bc
9-x^2/x^2+5x+6=(3+x)(3-x)/(x+2)(x+3)
9a^2(x+y)/3a(x+y)=3a
a^(n+2)-a^2b^n/a^(2n+1)-ab^2n=a^2(a^n-b^n)/a(a^n-b^n)(a^n+b^n)

（1）原式=9-1+5x+6
=14+5x
（2）原式=3a（分子分母公因式为3a（x+y））
（3）原式=a^n+2-a^2b^n/a^2n+1-ab^2n
=(a^n*a^2-a^2*b^n)/(a^2n*a-ab^2n)
...

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（1）原式=9-1+5x+6
=14+5x
（2）原式=3a（分子分母公因式为3a（x+y））
（3）原式=a^n+2-a^2b^n/a^2n+1-ab^2n
=(a^n*a^2-a^2*b^n)/(a^2n*a-ab^2n)
=a^2(a^n-b^n)/a(a^2n-b^2n)
=a^2(a^n-b^n)/a(a^n+b^n)(a^n-b^n)（注：a^2n-b^2n=(a^n)^2-(b^n)^2）
=a/(a^n+b^n)
（4）原式=-(x+y)(x-y)^2/-(x+y)^2(x-y)
=x-y/x+y
（5）原式=（a+b）^2-c^2/a^2-（b+c）^2
=（a+b-c）（a+b+c）/（a+b+c）（a-b-c）
=（a+b-c）/（a-b-c)

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(1)9-x^2/x^2+5x+6
=(3+x)(3-x)/(x+2)(x+3)
=(3-x)/(x+2)
(2)9a^2(x+y)/3a(x+y)
=3a
(3)a^(n+2)-a^2b^n/a^(2n+1)-ab^2n
=a^2(a^n-b^n)/a(a^n-b^n)(a^n+b^n)
=a/(a^n+b^n)
(4)-(x+y)...

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(1)9-x^2/x^2+5x+6
=(3+x)(3-x)/(x+2)(x+3)
=(3-x)/(x+2)
(2)9a^2(x+y)/3a(x+y)
=3a
(3)a^(n+2)-a^2b^n/a^(2n+1)-ab^2n
=a^2(a^n-b^n)/a(a^n-b^n)(a^n+b^n)
=a/(a^n+b^n)
(4)-(x+y)(x-y)^2/(y+x)(y^2-x^2)
=-(x+y)(x-y)(x-y)/(x+y)(x+y)(y-x)
=(x-y)/(x+y)
(5)a^2+b^2-c^2+2ab/a^2-b^2-c^2-2bc
=[(a+b)²-c²]/[a²-(b+c)²]
=(a+b+c)(a+b-c)/(a+b+c)(a-b-c)
=(a+b-c)/(a-b-c)

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