Let A be the matrix of quadratic form (x1- x2 + 2x3)2.Then, trace of A...
We are given that A be a matrix of quardratic form (x1-x2 + 2x3)2
or x12 + x22 + 4x32 - 2x1x2 - 4x2x3 + 4x3x1
trace (A) = sum of coefficient of
x12, x22 and x32.
= 1 + 1 + 4
= 6
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Let A be the matrix of quadratic form (x1- x2 + 2x3)2.Then, trace of A...
Quadratic Form:
A quadratic form is a homogeneous polynomial of degree 2 in the variables x1, x2, x3, etc. It can be represented as a matrix equation:
Q(x) = x^T * A * x
where x is a vector (x1, x2, x3, etc.) and A is a symmetric matrix.
Matrix of Quadratic Form:
To find the matrix A of the given quadratic form (x1 - x2 + 2x3)^2, we expand the expression and collect the coefficients of the variables:
Q(x) = (x1 - x2 + 2x3)^2
= x1^2 - 2x1x2 + 4x1x3 - 2x1x2 + x2^2 - 4x2x3 + 4x1x3 - 4x2x3 + 4x3^2
= x1^2 + x2^2 + 4x3^2 - 4x1x2 - 8x2x3 + 8x1x3
From this expression, we can see that the matrix A is:
A = [[1, -2, 4],
[-2, 1, -4],
[4, -4, 4]]
Trace of a Matrix:
The trace of a square matrix is the sum of its diagonal elements. In this case, the matrix A is a 3x3 symmetric matrix.
So, the trace of A is given by:
trace(A) = a11 + a22 + a33
where aij represents the elements of A.
Calculating the Trace:
Let's calculate the trace of A:
trace(A) = 1 + 1 + 4
= 6
Therefore, the correct answer is option 'C', which is 6.