Target Exam

CUET

Subject

-- Mathematics - Section B1

Chapter

Three-dimensional Geometry

Question:

The straight line \( \frac{x + 3}{3} = \frac{y + 2}{4} = \frac{z + 1}{0} \) is

Options:

Parallel to x-axis

Parallel to y-axis

Parallel to z-axis

Perpendicular to z-axis

Correct Answer:

Perpendicular to z-axis

Explanation:

The correct answer is Option (4) → Perpendicular to z-axis

Given line: $\displaystyle \frac{x + 3}{3} = \frac{y + 2}{4} = \frac{z + 1}{0}$

Since $\displaystyle \frac{z + 1}{0}$ is undefined, it implies $z + 1 = 0 \Rightarrow z = -1$

So the line lies entirely in the plane $z = -1$, i.e., it does not vary along the $z$-axis

Direction ratios of the line: $(3, 4, 0)$

This means the line is parallel to the vector $3\hat{i} + 4\hat{j}$ and has no $k$ component

⟹ The line lies in the $xy$-plane and is perpendicular to the $z$-axis