Exercise · ZW-LINES-AND-PLANES-IN-SPACE-007 · ★★☆ Intermediate
At which point does the line \((1+t,\,2-t,\,3+2t)\) meet the plane \(x+y+z=10\)?
Choose one option.
A \((2,1,5)\) B \((4,-1,9)\) C \((1,2,3)\) D \((3,0,7)\)
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Explanation Substituting, \((1+t)+(2-t)+(3+2t)=6+2t=10\), so \(t=2\). The point is \((3,0,7)\); the point \((1,2,3)\) corresponds to \(t=0\) and is not on the plane.
A line in space is determined by a point \(\mathbf r_0\) and a direction vector \(\mathbf d\); a plane, by a point \(\mathbf r_0\) and a normal vector \(\mathbf n\) perpendicular to it.
\[\begin{aligned}\mathbf r(t)&=\mathbf r_0+t\,\mathbf d\\\mathbf n\cdot(\mathbf r-\mathbf r_0)&=0\end{aligned}\]
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