Question:

The line passing through the points \((2,1,0) , (5,0,1)\) and \( (4,1,1)\) intersects the \(x-\)axis at

Updated On: Jul 31, 2023
  • \((3,0,0)\)

  • \((-3,0,0) \)

  • \((0,0,0)\)

  • \((1,0,0) \)

  • (-1,0,0)

  • \((5,0,0)\)

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Solution and Explanation

Given that

The given points are \((2, 1, 0), (5, 0, 1)\), and \((4, 1, 1)\)

Then to find where it intersects the \(x-\)axis, we first need to find the parametric equation of the line.

Let the parametric equation of the line be:

\(r = (2, 1, 0) + t × (a, b, c)\)

where \((2, 1, 0)\) is one of the given points, and \((a, b, c)\) is the direction vector of the line.

We can find the direction vector by subtracting one point from another. Let's choose \((5, 0, 1)\) and \((2, 1, 0)\):

Direction vector = \((5, 0, 1) - (2, 1, 0) = (3, -1, 1)\)

So, the parametric equation of the line is:

\(r = (2, 1, 0) + t × (3, -1, 1)\)

Now, to find where this line intersects the x-axis, we need to find the value of t when the y and z coordinates become zero. That means we need to solve the following system of equations:

  1. \(x = 2 + 3t\)
  2. \(y = 1 - t = 0\)
  3. \(z = t = 0\)

From equation (2), we find \(t = 1.\)

Now, substitute \(t = 1\),

into equation (1) to find the \(x-\)coordinate:

\(x = 2 + 3(1) = 5\)

So, the line intersects the \(x-\)axis at the point \((5, 0, 0).\) (_Ans)

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Concepts Used:

Equation of a Line in Space

In a plane, the equation of a line is given by the popular equation y = m x + C. Let's look at how the equation of a line is written in vector form and Cartesian form.

Vector Equation

Consider a line that passes through a given point, say ‘A’, and the line is parallel to a given vector '\(\vec{b}\)‘. Here, the line ’l' is given to pass through ‘A’, whose position vector is given by '\(\vec{a}\)‘.  Now, consider another arbitrary point ’P' on the given line, where the position vector of 'P' is given by '\(\vec{r}\)'.

\(\vec{AP}\)=𝜆\(\vec{b}\)

Also, we can write vector AP in the following manner:

\(\vec{AP}\)=\(\vec{OP}\)\(\vec{OA}\)

𝜆\(\vec{b}\) =\(\vec{r}\)\(\vec{a}\)

\(\vec{a}\)=\(\vec{a}\)+𝜆\(\vec{b}\)

\(\vec{b}\)=𝑏1\(\hat{i}\)+𝑏2\(\hat{j}\) +𝑏3\(\hat{k}\)