JEE Main 2025 April 2 Exam Analysis: Paper Difficulty Level and Topics

Equation of Straight Line - Practice Questions & MCQ

Edited By admin | Updated on Sep 18, 2023 18:34 AM | #JEE Main

Quick Facts

  • Equation of Straight Line (Part 1), Equation of Straight Line (Part 2), Normal and Parametric form of a line is considered one of the most asked concept.

  • 108 Questions around this concept.

Solve by difficulty

A ray of light along $x+\sqrt{3} y=\sqrt{3}$ gets reflected upon reaching $x$-axis ,the equation of the reflected ray is :

Let PS be the median of the triangle with vertices P(2, 2), Q(6,-1) and R(7, 3). The equation of the line passing through (1,-1) and parallel to PS is :

 

The equation of the line bisecting perpendicularly the segment joining the points (-4,6) and (8,8) is

Find the line which is equally inclined to $x+2 y-1=0$ and passes through $(0,2)$

 

Find which of the following points don't lie on the line 3x-y+2=0.

If a line passes through $\left ( -1,0 \right )$ and is inclined at an angle of $30^{o}$ with the position X-axis, find its slope-point form of the equation of a line in simplified form.

Which of the following is the correct diagram of line with slope $-\sqrt{3}$ ?

VIT - VITEEE 2025

National level exam conducted by VIT University, Vellore | Ranked #11 by NIRF for Engg. | NAAC A++ Accredited | Last Date to Apply: 31st March | NO Further Extensions!

UPES B.Tech Admissions 2025

Ranked #42 among Engineering colleges in India by NIRF | Highest CTC 50 LPA , 100% Placements

Write $3 x-y=2$ in slope interception form of the equation  of a line

A line passes through (2, 2) and is perpendicular to the line 3x + y = 3. Its y-intercept is
 

JEE Main 2025 - 10 Full Mock Test
Aspirants who are preparing for JEE Main can download JEE Main 2025 mock test pdf which includes 10 full mock test, high scoring chapters and topics according to latest pattern and syllabus.
Download EBook

If $a^4 b^4-a^4-b^4=2 a^2 b^2\{a, b \in R-\{0\}\}$, then the line $\frac{x}{a^2}+\frac{y}{b^2}=1$, will pass through

Concepts Covered - 3

Equation of Straight Line (Part 1)

Equation of Straight Line

(a) Slope-Intercept form

Consider the given figure

$A B$ is a straight line with slope $m$ and intercept $c$ on Y -axis. $\mathrm{P}(\mathrm{x}, \mathrm{y})$ any point on the straight line. PL is perpendicular to X -axis and MQ is perpendicular to Y -axis

$
\begin{aligned}
& \angle \mathrm{PRL}=\angle \mathrm{PQM}=\theta, \quad \mathrm{OQ}=\mathrm{c} \\
& \mathrm{PM}=\mathrm{PL}-\mathrm{ML}=\mathrm{PL}-\mathrm{OQ}=\mathrm{y}-\mathrm{c} \\
& \mathrm{QM}=\mathrm{OL}=\mathrm{x} \\
& \operatorname{In} \triangle \mathrm{PQM}, \tan \theta=\frac{\mathrm{PM}}{\mathrm{QM}}=\frac{\mathrm{y}-\mathrm{c}}{\mathrm{x}} \\
& \tan \theta=\mathrm{m}=\frac{\mathrm{y}-\mathrm{c}}{\mathrm{x}} \\
& \Rightarrow \mathrm{y}=\mathrm{mx}+\mathrm{c}
\end{aligned}
$
The equation of a straight line whose slope is given as $m$ and making $y$-intercept of length $c$ unit is $y=m x+c$.
If the straight line passing through the origin, then equation of straight line become $y=m x$
If Equation of straight line is $\mathrm{Ax}+\mathrm{By}+\mathrm{C}=0$, then
We can write $\mathrm{By}=-\mathrm{Ax}-\mathrm{C}$

$
\mathrm{y}=\left(-\frac{\mathrm{A}}{\mathrm{~B}}\right) \mathrm{x}+\left(-\frac{\mathrm{C}}{\mathrm{~B}}\right)
$

compare with $\mathrm{y}=\mathrm{mx}+\mathrm{c}$

$
\begin{aligned}
& \text { slope }=m=-\frac{A}{B} \\
& y-\text { intercept }=c=-\frac{C}{B}
\end{aligned}
$

(b) Point-Slope form

Let the equation of give line I with slope ' $m$ ' is

$
y=m x+c
$

$\left(x_1, y_1\right)$ lies on the line i

$
y_1=m x_1+c
$
From (i) and (ii) [(ii) - (i)]

$
y-y_1=m\left(x-x_1\right)
$
The equation of a straight line whose slope is given as ' $m$ ' and passes through the point $\left(x_1, y_1\right)$ is $\mathbf{y}-\mathbf{y}_1=\mathbf{m}\left(\mathbf{x}-\mathbf{x}_1\right)$

Equation of Straight Line (Part 2)

Equation of Straight Line

(c) Two-point form

The equation of a straight line passing through the two given points (x1,y1) and  (x2,y2) is  given by

$
\mathbf{y}-\mathbf{y}_1=\left(\frac{\mathbf{y}_2-\mathbf{y}_1}{\mathbf{x}_2-\mathbf{x}_1}\right)\left(\mathbf{x}-\mathbf{x}_1\right)
$
Proof:
Let the equation of straight line I with slope ' $m$ ' be

$
y=m x+c
$
Points $\left(\mathrm{x}_1, \mathrm{y}_1\right)$ and $\left(\mathrm{x}_2, \mathrm{y}_2\right)$ pass through the given line I , then

$
\begin{aligned}
& \mathrm{y}_1=\mathrm{mx}_1+\mathrm{c} \\
& \mathrm{y}_2=\mathrm{mx}_2+\mathrm{c}
\end{aligned}
$

$\qquad$
Subtract eq (ii) from eq (i)

$
y-y_1=m\left(x-x_1\right)
$
Subtract eq (iii) from eq (i)

$
\mathrm{y}-\mathrm{y}_2=\mathrm{m}\left(\mathrm{x}-\mathrm{x}_2\right)
$
Divide eq (iv) by eq ( $\mathbf{v}$ )

$
\begin{aligned}
& \frac{\mathrm{y}-\mathrm{y}_1}{\mathrm{y}_2-\mathrm{y}_1}=\frac{\mathrm{x}-\mathrm{x}_1}{\mathrm{x}_2-\mathrm{x}_1} \\
& \Rightarrow \mathrm{y}-\mathrm{y}_{\mathbf{1}}=\left(\frac{\mathrm{y}_2-\mathrm{y}_1}{\mathrm{x}_2-\mathrm{x}_1}\right)\left(\mathrm{x}-\mathrm{x}_{\mathbf{1}}\right) \\
& \text { also here } \mathrm{m}=\left(\frac{\mathrm{y}_2-\mathrm{y}_1}{\mathrm{x}_2-\mathrm{x}_1}\right)
\end{aligned}
$

Determinant Form:
If $\mathrm{P}(\mathrm{x}, \mathrm{y}), \mathrm{Q}\left(\mathrm{x}_1, \mathrm{y}_1\right)$ and $\mathrm{R}\left(\mathrm{x}_2, \mathrm{y}_2\right)$ are collinear, then area of $\triangle \mathrm{PQR}=0$
i.e. $\left.\quad \frac{1}{2}\left|\begin{array}{ccc}x & y & 1 \\ x_1 & y_1 & 1 \\ x_2 & y_2 & 1\end{array}\right| \right\rvert\,=0$
(d) Intercept form of line

Equation of a straight line which makes intercepts ' $a$ ' and 'b' on X -axis and Y -axis respectively is given by

$
\frac{\mathrm{x}}{\mathrm{a}}+\frac{\mathrm{y}}{\mathrm{~b}}=1
$
Proof:
A straight line which cut $X$-axis at $A(a, 0)$ and $Y$-axis at $B(0, b)$
Using the concept of two points form of a line
Equation of a straight line through the two-point $A(a, 0)$ and $B(0, b)$

$
\begin{aligned}
& y-0=\frac{b-0}{0-a}(x-a) \\
& \Rightarrow-a y=b x-a b \\
& \Rightarrow b x+a y=a b
\end{aligned}
$

divide LHS and RHS by ab

$
\frac{x}{a}+\frac{y}{b}=1
$
Note:

For the general equation $A x+B y+C=0$
If $\mathrm{C} \neq 0$, then $\mathrm{Ax}+\mathrm{By}+\mathrm{C}=0$ can be written as

$
\begin{aligned}
& A x+B y=-C \\
& \frac{x}{-\frac{C}{A}}+\frac{y}{-\frac{C}{B}}=1 \text { or } \frac{x}{a}+\frac{y}{b}=1
\end{aligned}
$

where, $\mathrm{a}=-\frac{\mathrm{C}}{\mathrm{A}}$ and $\mathrm{b}=-\frac{\mathrm{C}}{\mathrm{B}}$
Hence, $x$-intercept is $-\frac{\mathrm{C}}{\mathrm{A}}$ and $y$-intercept is $-\frac{\mathrm{C}}{\mathrm{B}}$

 

Normal and Parametric form of a line

Normal and Parametric form of a line

Normal form of line

Equation of straight line on which the length of the perpendicular from the origin is $p$ and this normal makes an angle $\theta$ with the positive direction of X -axis is given by

$
\mathbf{x} \cos \theta+\mathbf{y} \sin \theta=\mathbf{p}
$

Proof:
$A B$ is the straight line and length of perpendicular from origin to the line is p (i.e. $O N=p$ ).
Line $A B$ cuts $X$-axis and $Y$-axis at point $Q$ and $R$ respectively

$
\begin{aligned}
& \angle \mathrm{NOX}=\theta \\
& \angle \mathrm{NQO}=90^{\circ}-\theta \\
& \therefore \angle \mathrm{NQX}=180^{\circ}-\left(90^{\circ}-\theta\right)=90^{\circ}+\theta \\
& \text { Slope } m=\tan \left(90^{\circ}+\theta\right)=-\cot (\theta)
\end{aligned}
$
In triangle NOL

$
O L=x=p \cdot \cos \theta, N L=y=p \cdot \sin \theta
$
Point $N(p \cdot \cos \theta, p \cdot \sin \theta)$
Using Slope-point form, equation of line $A B$ is

$
\begin{aligned}
& y-p \cdot \sin \theta=-\frac{\cos \theta}{\sin \theta}(x-p \cdot \cos \theta) \\
& x \cdot \cos \theta+y \cdot \sin \theta=p
\end{aligned}
$

Parametric form of a line

The equation of a straight line passing through the point $\left(\mathrm{x}_1, \mathrm{y}_1\right)$ and making an angle $\theta$ with the positive direction of $X$-axis is

$
\frac{\mathrm{x}-\mathrm{x}_1}{\cos \theta}=\frac{\mathrm{y}-\mathrm{y}_1}{\sin \theta}=\mathrm{r}
$
Where $r$ is the directed distance between the points $(x, y)$ and $\left(x_1, y_1\right)$.
Proof:
$A B$ is a straight line passing through the point $P\left(x_1, y_1\right)$ and meets $X$-axis at $R$ and makes an angle $\theta$ with the positive direction of $X$-axis.

 

Let $Q(x, y)$ be any point on the line $A B$ at a distance ' $r$ ' from $P$
As from the figure

$
\begin{aligned}
& \mathrm{PN}=\mathrm{ML}=\mathrm{OL}-\mathrm{OM}=\mathrm{x}-\mathrm{x}_1 \\
& \mathrm{QN}=\mathrm{QL}-\mathrm{NL}=\mathrm{QL}-\mathrm{PM}=\mathrm{y}-\mathrm{y}_1 \\
& \mathrm{In} \triangle \mathrm{NPQ} \\
& \cos \theta=\frac{\mathrm{PN}}{\mathrm{PQ}}=\frac{\mathrm{x}-\mathrm{x}_1}{\mathrm{r}} \\
& \sin \theta=\frac{\mathrm{QN}}{\mathrm{PQ}}=\frac{\mathrm{y}-\mathrm{y}_1}{\mathrm{r}}
\end{aligned}
$
From the above two equation

$
\frac{x-x_1}{\cos \theta}=\frac{y-y_1}{\sin \theta}=r
$
Also,

$
\begin{aligned}
& \mathrm{x}=\mathrm{x}_1+\mathrm{r} \cos \theta \\
& \mathrm{y}=\mathrm{y}_1+\mathrm{r} \sin \theta
\end{aligned}
$

Parametric equations of straight line AB

Study it with Videos

Equation of Straight Line (Part 1)
Equation of Straight Line (Part 2)
Normal and Parametric form of a line

"Stay in the loop. Receive exam news, study resources, and expert advice!"

Books

Reference Books

Equation of Straight Line (Part 1)

Mathematics for Joint Entrance Examination JEE (Advanced) : Coordinate Geometry

Page No. : 2.1

Line : 9

Equation of Straight Line (Part 2)

Mathematics for Joint Entrance Examination JEE (Advanced) : Coordinate Geometry

Page No. : 2.3

Line : 32

E-books & Sample Papers

Get Answer to all your questions

Back to top