經濟數學的問題 - 經濟

※ 引述《JimmyWr (獨立與自由)》之銘言：
: 學校:東海
: 科目: 經濟動態分析方法與應用
: 教科書 Alpha Chiang
: 題目:
: Given a Qutratic Form u'Du, Where D is 2X2
: the characteristic equation of D can be written as
: | d11-r d12 |
: | d21 d22-r| =0 (d12=d21)
: Expand the determinant ; express the root of this equation by use of
: the qutratic formula; and deduce the following
: (a) No imagianry number can occur r1 and r2
: (b). to have repeated roots , matrix D must be in the form of [ c 0 ]
: [ 0 c ]
: (這是一個矩陣)
: (c) to have either positive or negatice semidefinateness ,
: the discriminant of the quadratic form may vanish , that is,
: |D|=o is possibele
: 我的想法: 請問第一個主要問題 將矩陣的determine值張開
: 是直接求determine的值嗎
是

: B和C題的題意不大了解 能否請各位高手解釋一下..

b: 重根時，D一定是長成這個樣子

c: 半正定或半負定時，D的行列式可能是0


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