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Match List-I with List-II

List-IList-II
Equation of lineInformation
(A) r⃗=(3i^−2j^+k^)+λ(j^−2k^)\vec{r} = (3\hat{i} - 2\hat{j} + \hat{k}) + \lambda(\hat{j} - 2\hat{k})(I) Direction ratios are 2, 4, -1
(B) 2−x1=2y+14\frac{2-x}{1} = \frac{2y+1}{4}, z=2z = 2(II) Perpendicular to 2i^−j^+k^2\hat{i} - \hat{j} + \hat{k}
(C) x1=y−32=3−4z2\frac{x}{1} = \frac{y-3}{2} = \frac{3-4z}{2}(III) Passing through the point (3,−2,1)(3, -2, 1)
(D) r⃗=(3i^+2j^+k^)+λ(2i^+j^−3k^)\vec{r} = (3\hat{i} + 2\hat{j} + \hat{k}) + \lambda(2\hat{i} + \hat{j} - 3\hat{k})(IV) Direction ratios are -1, 2, 0

Choose the correct answer from the options given below:

Solution

✅ Correct Option: 1

For vector form of a line r⃗=a⃗+λb⃗\vec{r} = \vec{a} + \lambda\vec{b}, the vector a⃗\vec{a} gives a point on the line and b⃗\vec{b} gives the direction ratios.

For Cartesian form x−x1a=y−y1b=z−z1c\frac{x-x_1}{a} = \frac{y-y_1}{b} = \frac{z-z_1}{c}, the direction ratios are a,b,ca, b, c.


For (A): r⃗=(3i^−2j^+k^)+λ(j^−2k^)\vec{r} = (3\hat{i} - 2\hat{j} + \hat{k}) + \lambda(\hat{j} - 2\hat{k})

Position vector =3i^−2j^+k^= 3\hat{i} - 2\hat{j} + \hat{k}

The line passes through point (3,−2,1)(3, -2, 1)

Direction vector =0i^+1j^−2k^= 0\hat{i} + 1\hat{j} - 2\hat{k}

Direction ratios: (0,1,−2)(0, 1, -2)

(A) matches with (III)


For (B): 2−x1=2y+14\frac{2-x}{1} = \frac{2y+1}{4}, z=2z = 2

Rewriting: 2−x1=x−2−1\frac{2-x}{1} = \frac{x-2}{-1}

2y+14=y+122\frac{2y+1}{4} = \frac{y+\frac{1}{2}}{2}

Since z=2z = 2 (constant), the direction ratio for zz is 00

Direction ratios: (−1,2,0)(-1, 2, 0)

(B) matches with (IV)


For (C): x1=y−32=3−4z2\frac{x}{1} = \frac{y-3}{2} = \frac{3-4z}{2}

Rewriting the z-term:

3−4z2\frac{3-4z}{2}

=−(4z−3)2= \frac{-(4z-3)}{2}

=4z−3−2= \frac{4z-3}{-2}

Direction ratios from the equation: (1,2,−12)(1, 2, -\frac{1}{2})

Multiplying by 22: (2,4,−1)(2, 4, -1)

(C) matches with (I)


For (D): r⃗=(3i^+2j^+k^)+λ(2i^+j^−3k^)\vec{r} = (3\hat{i} + 2\hat{j} + \hat{k}) + \lambda(2\hat{i} + \hat{j} - 3\hat{k})

Direction vector of line D =2i^+j^−3k^= 2\hat{i} + \hat{j} - 3\hat{k}

Two vectors are perpendicular if their dot product =0= 0

Dot product with 2i^−j^+k^2\hat{i} - \hat{j} + \hat{k}:

(2)(2)+(1)(−1)+(−3)(1)(2)(2) + (1)(-1) + (-3)(1)

=4−1−3= 4 - 1 - 3

=0= 0

The line is perpendicular to 2i^−j^+k^2\hat{i} - \hat{j} + \hat{k}

(D) matches with (II)


(A) - (III), (B) - (IV), (C) - (I), (D) - (II)

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