呜 十万火急呀!分式的题目,请从下列三个代数试中任意选两个够成一个分式,并化简该分式x^2-4xy+4y^2 x^2-4

x^2 - 4xy + 4y^2 = (x-2y)^2
x^2 - 4y^2 = (x-2y)(x+2y)
(x^2 - 4xy + 4y^2)/(x-2y) = (x-2y)^2/(x-2y) = x - 2y
(x^2 - 4y^2)/(x-2y) = (x-2y)(x+2y)/(x-2y) = x + 2y
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(a^2 - 9)/[(a+3)(a-4)],
a 不等于-3,a不等于4.
a = 3 时,(a^2 - 9)= 0
所以
a = 3 时,(a^2 - 9)/[(a+3)(a-4)]= 0
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小明说的不对,
(x^2 - 9)/(x+3）只有当x 不等于-3时,才有意义.
因此,
当 x 不等于-3时,
(x^2 - 9)/(x+3) = x - 3.
所以,
(x^2 - 9)/(x+3) 和x-3并不是等价的.
因此,
(x^2 - 9)/(x+3) 不是整式.

x^2 - 4xy + 4y^2 = (x-2y)^2
x^2 - 4y^2 = (x-2y)(x+2y)
(x^2 - 4xy + 4y^2)/(x-2y) = (x-2y)^2/(x-2y) = x - 2y
(x^2 - 4y^2)/(x-2y) = (x-2y)(x+2y)/(x-2y) = x + 2y

I don't know.