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JEE MATHEMATICS MCQ: MATRICES

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An nร—nn \times n matrix is formed using 0,1 and โˆ’1-1 as its elements. The number of such matrices which are skewsymmetric, is
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Correct option: D
3n(nโˆ’1)23^{\frac{n(n-1)}{2}}
Option D (3n(nโˆ’1)23^{\frac{n(n-1)}{2}}) is correct because each of the n(nโˆ’1)2\frac{n(n-1)}{2} elements above the diagonal can take 3 values (0, 1, -1), determining the rest of the skew-symmetric matrix.

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If โˆฃabโˆ’cb+cc+abcโˆ’aaโˆ’ba+bcโˆฃ=0\left|\begin{array}{ccc}a & b-c & b+c \\ c+a & b & c-a \\ a-b & a+b & c\end{array}\right|=0 and a,b,ca, b, c are real numbers then the line ax+by+c=0a x+b y+c=0 passes through the fixed point is The number of solutions of the system of equations x2โˆ’x3=1,โ€…โ€Šโˆ’x1+2x3=โˆ’2,โ€…โ€Šx1โˆ’2,โ€…โ€Šx1โˆ’2x2=3{x_2} - {x_3} = 1,\; - {x_1} + 2{x_3} = - 2,\;{x_1} - 2,\;{x_1} - 2{x_2} = 3 is If the equations 2x+3y+1=0,3x+yโˆ’2=02x + 3y + 1 = 0,3x + y - 2 = 0 and ax+2yโˆ’b=0ax + 2y - b = 0 are consistent, then The value of the determinant โˆฃ1(ฮฑ2xโˆ’ฮฑโˆ’2x)2(ฮฑ2x+ฮฑโˆ’2x)21(ฮฒ2xโˆ’ฮฒโˆ’2x)2(ฮฒ2x+ฮฒโˆ’2x)21(ฮณ2xโˆ’ฮณโˆ’2x)2(ฮณ2x+ฮณโˆ’2x)2โˆฃ\left|\begin{array}{ccc}1 & \left(\alpha^{2 x}-\alpha^{-2 x}\right)^2 & \left(\alpha^{2 x}+\alpha^{-2 x}\right)^2 \\ 1 & \left(\beta^{2 x}-\beta^{-2 x}\right)^2 & \left(\beta^{2 x}+\beta^{-2 x}\right)^2 \\ 1 & \left(\gamma^{2 x}-\gamma^{-2 x}\right)^2 & \left(\gamma^{2 x}+\gamma^{-2 x}\right)^2\end{array}\right|, is If ฯ‰\omega is the cube root of unity, then โˆฃ1ฯ‰ฯ‰2ฯ‰ฯ‰21ฯ‰21ฯ‰โˆฃ\left| {\begin{array}{cccccccccccccccccccc} 1&\omega &{{\omega ^2}}\\ \omega &{{\omega ^2}}&1\\ {{\omega ^2}}&1&\omega \end{array}} \right| is equal to For any matrix AA of order 2ร—22 \times 2, if A(adjโกA)=[100010]A(\operatorname{adj} A)=\left[\begin{array}{cc}10 & 0 \\ 0 & 10\end{array}\right], then โˆฃAโˆฃ|A| is equal to
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