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Given that Q = \(\begin{pmatrix} 6 & 0 \\ 4 & 5 \end{pmatrix}\) and Q...

Mathematics
JAMB 1999

Given that Q = \(\begin{pmatrix} 6 & 0 \\ 4 & 5 \end{pmatrix}\) and Q + P = \(\begin{pmatrix} 7 & -2 \\ 6 & 8 \end{pmatrix}\). Evaluate | Q + 2P|.

  • A. 90
  • B. 96
  • C. 102
  • D. 120
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Correct Answer: Option D
Explanation

Q + 2P = Q + 2(Q + P - Q) = 2(Q + P) - Q

Q + P = \(\begin{pmatrix} 7 & -2 \\ 6 & 8 \end{pmatrix}\)

2(Q + P) = \(\begin{pmatrix} 14 & -4 \\ 12 & 16 \end{pmatrix}\)

Q + 2P = 2(Q + P) - Q = \(\begin{pmatrix} 14-6 & -4-0 \\ 12-4 & 16-5 \end{pmatrix} = \begin{pmatrix} 8 & -4 \\ 8 & 11 \end{pmatrix}\)

Determinant:  |Q + 2P| = 8 \(\times\) 11 - (-4)\(\times\) 8 = 88 + 32 = 120.


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Post-UTME Past Questions - Original materials are available here - Download PDF for your school of choice + 1 year SMS alerts
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Post-UTME Past Questions - Original materials are available here - Download PDF for your school of choice + 1 year SMS alerts
Post UTME Past Questions Agent