作业帮若xy=1,x+y=2,求1/4x^2-1/2xy+1/4y^2的值(1/4)(x-y)^2 =(1/4)[(x+y)^2-4xy] 这一步怎么来的?
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![若xy=1,x+y=2,求1/4x^2-1/2xy+1/4y^2的值(1/4)(x-y)^2 =(1/4)[(x+y)^2-4xy] 这一步怎么来的?](/uploads/image/z/8623221-69-1.jpg?t=%E8%8B%A5xy%3D1%2Cx%2By%3D2%2C%E6%B1%821%2F4x%5E2-1%2F2xy%2B1%2F4y%5E2%E7%9A%84%E5%80%BC%281%2F4%29%28x-y%29%5E2+%3D%281%2F4%29%5B%28x%2By%29%5E2-4xy%5D+%E8%BF%99%E4%B8%80%E6%AD%A5%E6%80%8E%E4%B9%88%E6%9D%A5%E7%9A%84%3F)
若xy=1,x+y=2,求1/4x^2-1/2xy+1/4y^2的值(1/4)(x-y)^2 =(1/4)[(x+y)^2-4xy] 这一步怎么来的?
若xy=1,x+y=2,求1/4x^2-1/2xy+1/4y^2的值
(1/4)(x-y)^2
=(1/4)[(x+y)^2-4xy]
这一步怎么来的?
若xy=1,x+y=2,求1/4x^2-1/2xy+1/4y^2的值(1/4)(x-y)^2 =(1/4)[(x+y)^2-4xy] 这一步怎么来的?
[(x+y)^2-4xy] =x^2+2xy+y^2-4xy
=x^2-2xy+y^2
=(x-y)^2