JEE MAIN - Mathematics (2023 - 13th April Evening Shift - No. 6)

The line, that is coplanar to the line $$\frac{x+3}{-3}=\frac{y-1}{1}=\frac{z-5}{5}$$, is :
$$\frac{x+1}{-1}=\frac{y-2}{2}=\frac{z-5}{4}$$
$$\frac{x+1}{-1}=\frac{y-2}{2}=\frac{z-5}{5}$$
$$\frac{x-1}{-1}=\frac{y-2}{2}=\frac{z-5}{5}$$
$$\frac{x+1}{1}=\frac{y-2}{2}=\frac{z-5}{5}$$

Explanation

Given two lines:

$\frac{x - x_1}{a_1} = \frac{y - y_1}{b_1} = \frac{z - z_1}{c_1}$

and

$\frac{x - x_2}{a_2} = \frac{y - y_2}{b_2} = \frac{z - z_2}{c_2}$

These lines are coplanar if the determinant of the matrix

$$ \begin{vmatrix} x_2-x_1 & y_2-y_1 & z_2-z_1 \\ a_1 & b_1 & c_1 \\ a_2 & b_2 & c_2 \end{vmatrix} $$ = 0

Now let's apply this condition to the given problem. The given line is :

$\frac{x + 3}{-3} = \frac{y - 1}{1} = \frac{z - 5}{5}$

So, the coordinates of any point on this line are $(-3, 1, 5)$ and the direction ratios are $(-3, 1, 5)$.

Now, let's calculate the determinants for each option and check which one equals zero.

For Option A :

$\frac{x + 1}{-1} = \frac{y - 2}{2} = \frac{z - 5}{4}$

The coordinates of any point on this line are $(-1, 2, 5)$ and the direction ratios are $(-1, 2, 4)$.

The determinant is :

$$ \begin{vmatrix} -1 - (-3) & 2 - 1 & 5 - 5 \\ -3 & 1 & 5 \\ -1 & 2 & 4 \end{vmatrix} = \begin{vmatrix} 2 & 1 & 0 \\ -3 & 1 & 5 \\ -1 & 2 & 4 \end{vmatrix} $$

Applying the formula :

= $2(1 \times 4 - 5\times2) - 1((-3\times4) - (5\times-1)) + 0((-3\times2) - (1\times-1))$

= $2(4 - 10) - 1(-12 - (-5)) + 0(-6 - (-1))$

= $2(-6) - 1(-7) + 0(-5)$

= $-12 + 7 + 0$

= $-5$

The determinant for Option A is not equal to zero, so this line is not coplanar with the given line.

For Option B, we have :

$\frac{x + 1}{-1} = \frac{y - 2}{2} = \frac{z - 5}{5}$

The coordinates of any point on this line are $(-1, 2, 5)$ and the direction ratios are $(-1, 2, 5)$.

$$ \begin{vmatrix} -1 - (-3) & 2 - 1 & 5 - 5 \\ -3 & 1 & 5 \\ -1 & 2 & 5 \end{vmatrix} = \begin{vmatrix} 2 & 1 & 0 \\ -3 & 1 & 5 \\ -1 & 2 & 5 \end{vmatrix} $$

Applying the formula, we get :

= $2(1*5 - 5*2) - 1((-3*5) - (5*-1)) + 0((-3*2) - (1*-1))$

= $2(5 - 10) - 1(-15 - (-5)) + 0(-6 - (-1))$

= $2(-5) - 1(-10) + 0(-5)$

= $-10 + 10 + 0$

= $0$

So, the determinant for Option B equals zero, which confirms that the line in Option B is coplanar with the given line.

For Option C :

$\frac{x - 1}{-1} = \frac{y - 2}{2} = \frac{z - 5}{5}$

The coordinates of any point on this line are $(1, 2, 5)$ and the direction ratios are $(-1, 2, 5)$.

The determinant is:

$$ \begin{vmatrix} 1 - (-3) & 2 - 1 & 5 - 5 \\ -3 & 1 & 5 \\ -1 & 2 & 5 \end{vmatrix} = \begin{vmatrix} 4 & 1 & 0 \\ -3 & 1 & 5 \\ -1 & 2 & 5 \end{vmatrix} $$

Applying the formula :

= $4(1*5 - 5*2) - 1((-3*5) - (5*-1)) + 0((-3*2) - (1*-1))$

= $4(5 - 10) - 1(-15 - (-5)) + 0(-6 - (-1))$

= $4(-5) - 1(-10) + 0(-5)$

= $-20 + 10 + 0$

= $-10$

The determinant for Option C is not equal to zero, so this line is not coplanar with the given line.

For Option D :

$\frac{x + 1}{1} = \frac{y - 2}{2} = \frac{z - 5}{5}$

The coordinates of any point on this line are $(-1, 2, 5)$ and the direction ratios are $(1, 2, 5)$.

The determinant is :

$$ \begin{vmatrix} -1 - (-3) & 2 - 1 & 5 - 5 \\ -3 & 1 & 5 \\ 1 & 2 & 5 \end{vmatrix} = \begin{vmatrix} 2 & 1 & 0 \\ -3 & 1 & 5 \\ 1 & 2 & 5 \end{vmatrix} $$

Applying the formula :

= $2(1*5 - 5*2) - 1((-3*5) - (5*1)) + 0((-3*2) - (1*1))$

= $2(5 - 10) - 1(-15 - 5) + 0(-6 - 1)$

= $2(-5) - 1(-20) + 0(-7)$

= $-10 + 20 + 0$

= $10$

So the determinant for Option D is not equal to zero, which means the line in Option D is not coplanar with the given line.

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