Q207 / 270 · NDA 2022 (Phase 2) · Mathematics
If $P(3,4)$ is the mid-point of a line segment between the axes, then what is the equation of the line?
- A$3 x+4 y-25=0$
- Correct answerB$4 x+3 y-24=0$
- C$4 x-3 y=0$
- D$3 x-4 y+7=0$
Solution
Concept:
- Midpoint of $\left(\mathrm{x}_1, \mathrm{y}_1\right)$ and $\left(\mathrm{x}_2, \mathrm{y}_2\right)=\left(\frac{x_1+x_2}{2}, \frac{y_1+y_2}{2}\right)$
- The equation of the line passing through $\left(x_1, y_1\right)$ and $\left(x_2, y_2\right)$ is
$\left(y-y_1\right)=\frac{y_2-y_1}{x_2-x_1}\left(x-x_1\right)$
Calculation:
Let the points of line on axes be $(h, 0)$ and $(0, k)$ respectively
So, $P(3,4)$ is the mid-point of $(h, 0)$ and $(0, k)$
$\begin{aligned}
& \Rightarrow(3,4)=\left(\frac{h+0}{2}, \frac{0+k}{2}\right) \\
& \Rightarrow \mathrm{h}=6 \text { and } \mathrm{k}=8
\end{aligned}$
So, the line passes through the points $(6,0)$ and $(0,8)$
$\Rightarrow$ The equation of the line passing through $(6,0)$ and $(0,8)$ is
$\begin{aligned}
& (y-0)=\frac{8-0}{0-6}(x-6) \\
& \Rightarrow-6 y=8 x-48 \\
& \Rightarrow 4 x+3 y-24=0
\end{aligned}$
Hence, the correct answer is option: 'B'.