求实二次型f(x1,x2,x3,x4)=x1^2+x2^2+x3^2+x4^2+2x1x2-2x1x4-2x2x3+2x3x4的规_其他解答

求实二次型f(x1,x2,x3,x4)=x1^2+x2^2+x3^2+x4^2+2x1x2-2x1x4-2x2x3+2x3x4的规范型

人气：290 ℃　时间：2020-02-05 20:37:51

解答

x1^2+x2^2+x3^2+x4^2+2x1x2+2x2x3+2x3x4
= (x1+x2)^2+x3^2+x4^2+2x2x3+2x3x4
= (x1+x2)^2+(x3+x4)^2+2x2x3
= y1^2+y2^2+2y3^2-2y4^2
= z1^2+z2^2+z3^2-z4^2