The co-ordinates of the points on the line $2 x-y=5$ which are the distance of 1 unit from the line $3 x+4…

The co-ordinates of the points on the line $2 x-y=5$ which are the distance of 1 unit from the line $3 x+4 y=5$ are
  1. $\left(\frac{30}{11}, \frac{-5}{11}\right),\left(\frac{20}{11}, \frac{15}{11}\right)$
  2. $\left(\frac{-30}{11}, \frac{5}{11}\right),\left(\frac{-20}{11}, \frac{15}{11}\right)$
  3. $\left(\frac{30}{11}, \frac{5}{11}\right),\left(\frac{20}{11}, \frac{-15}{11}\right)$
  4. $\left(\frac{-30}{11}, \frac{5}{11}\right),\left(\frac{-20}{11}, \frac{-15}{11}\right)$

Solution

Let $\left(x_1, y_1\right)$ be the required point $\therefore \quad 2 x_1-y_1=5$ Also, $\left(x_1, y_1\right)$ is at the distance of 1 unit from line $3 x+4 y=5$ $\begin{array}{ll} \therefore & 1=\left|\frac{3 x_1+4 y_1-5}{\sqrt{9+16}}\right| \\ \therefore & \pm 5=3 x_1+4 y_1-5 \\ \therefore & 3 x_1+4 y_1-5=5 \quad \text { or } 3 x_1+4 y_1-5=-5 \\ \therefore & 3 x_1+4 y_1=10 \\ & \text { or } \\ & 3 x_1+4 y_1=0 \end{array}$ Solving equations (i) and (ii), we get $x_1=\frac{30}{11}$ and $y_1=\frac{5}{11}$ Solving equation (i) and (iii), we get $x_1=\frac{20}{11}$ and $y_1=\frac{-15}{11}$ $\therefore \quad\left(\frac{30}{11}, \frac{5}{11}\right)$ and $\left(\frac{20}{11}, \frac{-15}{11}\right)$ are the required points.

Asked in: MHT CET 2023 (12 May Shift 1)

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