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$\mathrm{with}\left(\mathrm{geom3d}\right)\:$

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$\mathrm{point}\left(A\,0\,0\,0\right),\mathrm{point}\left(B\,1\,2\,3\right)\:$

Define the line that passes through two points A and B
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$\mathrm{line}\left(l\,\left[A\,B\right]\right)$

The equation of l is:
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$\mathrm{Equation}\left(l\,m\right)$

$\left[{m}{\,}{2}{}{m}{\,}{3}{}{m}\right]$
 (2) 
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$\mathrm{point}\left(C\,3\,7\,11\right)\:$

Define the plane that passes through three given points A, B, C
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$\mathrm{plane}\left(p\,\left[A\,B\,C\right]\,\left[a\,b\,c\right]\right)\:$

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$\mathrm{Equation}\left(p\right)$

${a}{}{2}{}{b}{+}{c}{=}{0}$
 (3) 