Question:

The value of x, so that the matrix $=\begin{bmatrix} x+a &b& c \\[0.3em] a& x+b & c \\[0.3em] a & b & x+c \end{bmatrix}$ has rank 3 , is

Updated On: Jul 7, 2022
  • $x\neq 0$
  • x = a + b + c
  • $x\neq\,0\, $ and $\,x\neq -(a+b+c) $
  • $x = 0$ and $ a = a + b+ c .$
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The Correct Option is C

Solution and Explanation

Since rank = 3. $\therefore$ $\begin{vmatrix}x+a&b&c\\ a&a+b&c\\ a&b&x+c\end{vmatrix} \ne 0 $ Operate $C_1 + C_2 + C_3$ $\begin{vmatrix}x+a+b+c&b&c\\ x+a+b+c&x+b&c\\ x+a+b+c&b&x+c\end{vmatrix} \neq 0 $ $\Rightarrow$ $(x + a + b + c) \begin{vmatrix}1&b&c\\ 1&x+b&c\\ 1&b&x+c\end{vmatrix} \neq 0$ $\Rightarrow$ $x + a +b + c \, \neq 0$ and $\begin{vmatrix}1&b&c\\ 0&x&0\\ 0&0&x\end{vmatrix} \ne 0 \Rightarrow x^{2} \ne 0 \Rightarrow x \ne 0$ Then $x \neq 0, x + a + b + c \neq 0$ $i.e., x \neq -(a + b + c)$
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Concepts Used:

Matrices

Matrix:

A matrix is a rectangular array of numbers, variables, symbols, or expressions that are defined for the operations like subtraction, addition, and multiplications. The size of a matrix is determined by the number of rows and columns in the matrix.

The basic operations that can be performed on matrices are:

  1. Addition of Matrices - The addition of matrices addition can only be possible if the number of rows and columns of both the matrices are the same.
  2. Subtraction of Matrices - Matrices subtraction is also possible only if the number of rows and columns of both the matrices are the same.
  3. Scalar Multiplication - The product of a matrix A with any number 'c' is obtained by multiplying every entry of the matrix A by c, is called scalar multiplication. 
  4. Multiplication of Matrices - Matrices multiplication is defined only if the number of columns in the first matrix and rows in the second matrix are equal. 
  5. Transpose of Matrices - Interchanging of rows and columns is known as the transpose of matrices.