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If A=[x+z2−3x043x−y0]A = \begin{bmatrix} x+z & 2 & -3 \\ x & 0 & 4 \\ 3 & x-y & 0 \end{bmatrix} is a skew-symmetric matrix, then which of the following are true?

(A) y>z>xy > z > x

(B) x>yx > y

(C) x+y+z>0x + y + z > 0

(D) z>xz > x

Choose the correct answer from the options given below:

Solution

✅ Correct Option: 4

A matrix is skew-symmetric if AT=−AA^T = -A

This means:

  1. All diagonal elements = 0
  2. Element at position (i,j) = -Element at position (j,i)

Given matrix: A=[x+z2−3x043x−y0]A = \begin{bmatrix} x+z & 2 & -3 \\ x & 0 & 4 \\ 3 & x-y & 0 \end{bmatrix}

The diagonal elements are: (x+z),0,0(x+z), 0, 0

For skew-symmetric property:

x+z=0x + z = 0

z=−xz = -x ... (Equation 1)


For element (1,2) and (2,1):

Element at (1,2) = 2

Element at (2,1) = xx

2=−x2 = -x

x=−2x = -2


For element (2,3) and (3,2):

Element at (2,3) = 4

Element at (3,2) = x−yx - y

4=−(x−y)4 = -(x - y)

4=−x+y4 = -x + y

y=4+xy = 4 + x ... (Equation 2)


From x=−2x = -2:

z=−xz = -x

z=−(−2)z = -(-2)

z=2z = 2

y=4+xy = 4 + x

y=4+(−2)y = 4 + (-2)

y=2y = 2

Final values: x=−2,y=2,z=2x = -2, y = 2, z = 2


(A) y>z>xy > z > x → 2>2>−22 > 2 > -2 → FALSE (yy is not greater than zz)

(B) x>yx > y → −2>2-2 > 2 → FALSE

(C) x+y+z>0x + y + z > 0 → −2+2+2=2>0-2 + 2 + 2 = 2 > 0 → TRUE

(D) z>xz > x → 2>−22 > -2 → TRUE


Both statements (C) and (D) are true.

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