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JAMB 2017 · UTME · Q17

If M=(13245−1−320)M = \begin{pmatrix} 1 & 3 & 2 \\ 4 & 5 & -1 \\ -3 & 2 & 0 \end{pmatrix} and N=(1−234−152−3−1)N = \begin{pmatrix} 1 & -2 & 3 \\ 4 & -1 & 5 \\ 2 & -3 & -1 \end{pmatrix}, evaluate 2M−3N2M - 3N.

Worked solution (try it first)
  1. Work entry by entry: each entry is 2×(entry of M)−3×(entry of N)2 \times (\text{entry of } M) - 3 \times (\text{entry of } N).
  2. Row 1: 2−3=−12 - 3 = -1, 6+6=126 + 6 = 12 and 4−9=−54 - 9 = -5.
  3. Row 2: 8−12=−48 - 12 = -4, 10+3=1310 + 3 = 13 and −2−15=−17-2 - 15 = -17.
  4. Row 3: −6−6=−12-6 - 6 = -12, 4+9=134 + 9 = 13 and 0+3=30 + 3 = 3.
  5. So 2M−3N2M - 3N is option C.

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