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.

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  • D. \((3,0,7)\)

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.

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Review the concept: Lines and planes in space

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.

\[\begin{aligned}\mathbf r(t)&=\mathbf r_0+t\,\mathbf d\\\mathbf n\cdot(\mathbf r-\mathbf r_0)&=0\end{aligned}\]

More practice problems: lines and planes in space

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