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Question

Question: If \(\mathbf{a} = - 3\mathbf{i} + 7\mathbf{j} + 5\mathbf{k},\) \(\mathbf{b} = - 3\mathbf{i} + 7\math...

If a=3i+7j+5k,\mathbf{a} = - 3\mathbf{i} + 7\mathbf{j} + 5\mathbf{k}, b=3i+7j3k\mathbf{b} = - 3\mathbf{i} + 7\mathbf{j} - 3\mathbf{k}, c=7i5j3k\mathbf{c} = 7\mathbf{i} - 5\mathbf{j} - 3\mathbf{k} are the three coterminous edges of a parallelopiped, then its volume is

A

108

B

210

C

272

D

308

Answer

272

Explanation

Solution

Volume $= \left| \begin{matrix}

  • 3 & 7 & 5 \
  • 3 & 7 & - 3 \ 7 & - 5 & - 3 \end{matrix} \right|$

=3(2115)7(9+21)+5(1549)= - 3( - 21 - 15) - 7(9 + 21) + 5(15 - 49)

=180210170=272= 180 - 210 - 170 = 272.