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If A=[5324]A = \begin{bmatrix} 5 & 3 \\ 2 & 4 \end{bmatrix}, then the matrix A26A+14A^2 - 6A + 14 I is (where I is an identity matrix of order 2)

Solution

Correct Option: 4

Given A=[5324]A = \begin{bmatrix} 5 & 3 \\ 2 & 4 \end{bmatrix}

Calculate A2A^2:

A2=[5324]×[5324]A^2 = \begin{bmatrix} 5 & 3 \\ 2 & 4 \end{bmatrix} \times \begin{bmatrix} 5 & 3 \\ 2 & 4 \end{bmatrix}

Position (1,1): (5)(5)+(3)(2)=25+6=31(5)(5) + (3)(2) = 25 + 6 = 31

Position (1,2): (5)(3)+(3)(4)=15+12=27(5)(3) + (3)(4) = 15 + 12 = 27

Position (2,1): (2)(5)+(4)(2)=10+8=18(2)(5) + (4)(2) = 10 + 8 = 18

Position (2,2): (2)(3)+(4)(4)=6+16=22(2)(3) + (4)(4) = 6 + 16 = 22

A2=[31271822]A^2 = \begin{bmatrix} 31 & 27 \\ 18 & 22 \end{bmatrix}


Calculate 6A6A:

6A=6×[5324]6A = 6 \times \begin{bmatrix} 5 & 3 \\ 2 & 4 \end{bmatrix}

6A=[30181224]6A = \begin{bmatrix} 30 & 18 \\ 12 & 24 \end{bmatrix}


Calculate 14I14I where I=[1001]I = \begin{bmatrix} 1 & 0 \\ 0 & 1 \end{bmatrix}:

14I=14×[1001]14I = 14 \times \begin{bmatrix} 1 & 0 \\ 0 & 1 \end{bmatrix}

14I=[140014]14I = \begin{bmatrix} 14 & 0 \\ 0 & 14 \end{bmatrix}


Calculate A26A+14IA^2 - 6A + 14I:

A26A+14I=[31271822][30181224]+[140014]A^2 - 6A + 14I = \begin{bmatrix} 31 & 27 \\ 18 & 22 \end{bmatrix} - \begin{bmatrix} 30 & 18 \\ 12 & 24 \end{bmatrix} + \begin{bmatrix} 14 & 0 \\ 0 & 14 \end{bmatrix}

Position (1,1): 3130+14=1531 - 30 + 14 = 15

Position (1,2): 2718+0=927 - 18 + 0 = 9

Position (2,1): 1812+0=618 - 12 + 0 = 6

Position (2,2): 2224+14=1222 - 24 + 14 = 12

A26A+14I=[159612]A^2 - 6A + 14I = \begin{bmatrix} 15 & 9 \\ 6 & 12 \end{bmatrix}

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