Question 513 Marks
Find the distance of the point (1, 2) from the straight line with slope 5 and passing through the point of intersection of x + 2y = 5 and x - 3y = 7.
Answer
View full question & answer→On solving x + 2y = 5 and x - 3y = 7 we get a point $\text{A}\Big(\frac{29}{5},\frac{-2}{5}\Big)$
The line passing through $\text{A}\Big(\frac{29}{5},\frac{-2}{5}\Big)$ and slope 5 is
$\text{y}+\frac{2}{5}=5\Big(\text{x}-\frac{29}{5}\Big)$
$5\text{y}+2=25\text{x}-145$
$25\text{x}-5\text{y}-147=0$
The distance of (1, 2) from 25x -5y - 147 = 0 is
$\Rightarrow\Big|\frac{25(1)-5(2)-147}{\sqrt{25^2+5^2}}\Big|$ [using distance formula]
$\Rightarrow\Big|\frac{-132}{\sqrt{650}}\Big|$
$\Rightarrow\Big|\frac{132}{\sqrt{650}}\Big|$
The line passing through $\text{A}\Big(\frac{29}{5},\frac{-2}{5}\Big)$ and slope 5 is
$\text{y}+\frac{2}{5}=5\Big(\text{x}-\frac{29}{5}\Big)$
$5\text{y}+2=25\text{x}-145$
$25\text{x}-5\text{y}-147=0$
The distance of (1, 2) from 25x -5y - 147 = 0 is
$\Rightarrow\Big|\frac{25(1)-5(2)-147}{\sqrt{25^2+5^2}}\Big|$ [using distance formula]
$\Rightarrow\Big|\frac{-132}{\sqrt{650}}\Big|$
$\Rightarrow\Big|\frac{132}{\sqrt{650}}\Big|$
Point (h, k) divides the line segment in the ratio 1 : 2