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39
MCQ (Single Correct Answer)

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

A
$\frac{1}{3}$
B
$\frac{2}{3}$
C
1
D
$\frac{4}{3}$
40
MCQ (Single Correct Answer)

The ratio in which the line $3 x+4 y+2=0$ divides the distance between the lines $3 x+4 y+5=0$ and $3 x+4 y-5=0$ is

A
$1: 2$
B
$3: 7$
C
$2: 3$
D
$2: 5$
41
MCQ (Single Correct Answer)

One vertex of the equilateral triangle with centroid at the origin and one side as $x+y-2=0$ is

A
$(-1,-1)$
B
$(2,2)$
C
$(-2,-2)$
D
$(2,-2)$
42

If $a, b$ and $c$ are in AP, then the straight lines $a x+b y+c=0$ will always pass through .............. .

Explanation

Given line is $$a x+b y+c=0\quad \text{.... (i)}$$

Since, $a, b$ and $c$ are in AP, then

$$\begin{aligned} b & =\frac{a+c}{2} \\ a-2 b+c & =0\quad \text{.... (ii)} \end{aligned}$$

On comparing Eqs.(i) and (ii), we get

$$x=1, y=2\quad \text{[using value of b in Eq. (i)]}$$

So, $(1,-2)$ lies on the line.

43

The line which cuts off equal intercept from the axes and pass through the point $(1,-2)$ is ............ .

Explanation

Let equation of line is

$$\frac{x}{a}+\frac{y}{a}=1\quad\text{.... (i)}$$

Since, this line passes through $(1,-2)$.

$$\begin{aligned} & \frac{1}{a}-\frac{2}{a}=1 \\ \Rightarrow \quad & 1-2=a \Rightarrow a=-1 \end{aligned}$$

$\therefore$ Required equation of the line is

$$\begin{aligned} -x-y & =1 \\ \Rightarrow \quad x+y+1 & =0 \end{aligned}$$