Find the distance between a point (– 2, 3 – 4) and its image on the plane x+y+z=3 measured parallel to a line
(x + 2)/3 = (2y + 3)/4 = (3z + 4)/5

Answer :

Answer:

The distance is:  

[tex]\displaystyle\frac{3\sqrt{142}}{10}[/tex]

Step-by-step explanation:

We re-write the equation of the line in the format:

[tex]\displaystyle\frac{x+2}{3}=\frac{y+\frac{3}{2}}{2}=\frac{z+\frac{4}{3}}{\frac{5}{3}} [/tex]

Notice we divided the fraction of y by 2/2, and the fraction of z by 3/3.

In that equation, the director vector of the line is built with the denominators of the equation of the line, thus:

[tex]\displaystyle\vec{v}=\left< 3, 2, \frac{5}{3}\right> [/tex]

Then the parametric equations of the line along that vector and passing through the point (-2, 3, -4) are:

[tex]x=-2+3t\\y=3+2t\\\displaystyle z=-4+\frac{5}{3}t[/tex]

We plug them into the equation of the plane to get the intersection of that line and the plane, since that intersection is the image on the plane of the point (-2, 3, -4)  parallel to the given line:

[tex]\displaystyle x+y+z=3\to -2+3t+3+2t-4+\frac{5}{3}t=3[/tex]

Then we solve that equation for t, to get:

[tex]\displaystyle \frac{20}{3}t-3=3\to t=\frac{9}{10}[/tex]

Then plugging that value of t into the parametric equations of the line we get the coordinates of the intersection:

[tex]\displaystyle x=-2+3\left(\frac{9}{10}\right)=\frac{7}{10}\\\displaystyle y=3+2\left(\frac{9}{10}\right)=\frac{24}{5} \\\displaystyle z=-4+\frac{5}{3}\left(\frac{9}{10}\right)=-\frac{5}{2}[/tex]

Then to find the distance we just use the distance formula:

[tex]\displaystyle d=\sqrt{(x_1-x_2)^2+(y_1-y_2)^2+(z_1-z_2)^2}[/tex]

So we get:

[tex]\displaystyle d=\sqrt{\left(-2-\frac{7}{10}\right)^2+\left(3-\frac{24}{5}\right)^2+\left(-4 +\frac{5}{2}\right)^2}=\frac{3\sqrt{142}}{10}[/tex]

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