形如f=x1x2+x2x3+x3x4的二次型化标准型,为什么设x1=y1+y2,x2=y1-y2,x3=y3,x4=y4看到书上写的是x1x2存在
人气：218 ℃ 时间：2020-05-13 19:37:52
解答
这样设是为了凑出平方项
x1x2 = (y1+y2)(y1-y2) = y1^2-y2^2
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