Matrices and Determinants 4 Question 32

33. Given, x=cy+bz,y=az+cx,z=bx+ay, where x,y, z are not all zero, prove that a2+b2+c2+2ab=1.

(1978,2M)

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Solution:

  1. Given systems of equations can be rewritten as x+cy+by=0,cxy+az=0 and bx+ayz=0

Above system of equations are homogeneous equation. Since, x,y and z are not all zero, so it has non-trivial solution.

Therefore, the coefficient of determinant must be zero.

|1cbc1aba1|=0

1(1a2)c(cab)+b(ca+b)=0

a2+b2+c2+2abc1=0

a2+b2+c2+2abc=1



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