此題用配方法即可.令x1=y1+y2,x2=y1-y2,y3=x3 則f = (y1+y2)(y1-y2)+(y1+y2)y3-3(y1-y2)y3= y1^2-y2^2-2y1y3+4y2y3= (y1-y3)^2-y2^2-y3^3+4y2y3= (y1-y3)^2 - (y2-2y3)^2 + 3y3^2令 z1=y1-y2,z2=y2-2y3,z3=y3,則f = ...首先謝謝您~但是還是想追問一下~應該令Z1=y1-y3吧？不是Z1=Y1-Y2吧~然后C2是怎么求出來的？我求的是C2=1 0 -10 1 20 0 1之后X和Z是怎么變得就沒看懂，為什么是C2C1^-1？？？謝謝，麻煩了~第7行筆誤 應該是 令 z1=y1-y3, z2=y2-2y3,z3=y3, 則....不好意思, 對應 C2 =1 0 -10 1 -200 1因為1. (x1,x2,x3)' =C1 (y1,y2,y3)' 2. (z1,z2,z3)' = C2(y1,y2,y3)'由2得 C2^-1(z1,z2,z3)' = (y1,y2,y3)'代入1中得 (x1,x2,x3)' =C1 (y1,y2,y3)'= C1C2^-1(z1,z2,z3)' 不好意思了哈