Find the equation of the line which passes through the point (– 4, 3) and the portion of the line intercepted between the axes is divided internally in the ratio 5 : 3 by this point.
Let $A B$ be a line passing through a point $(-4,3)$ and meets $x$-axis at $A(a, 0)$ and $y$-axis at $B(0, b)$
Using the section formula for internal division, we have
$(\mathrm{x}, \mathrm{y})=\left(\frac{\mathrm{m}_{1} \mathrm{x}_{2}+\mathrm{m}_{2} \mathrm{x}_{1}}{\mathrm{~m}_{1}+\mathrm{m}_{2}}, \frac{\mathrm{m}_{1} \mathrm{y}_{2}+\mathrm{m}_{2} \mathrm{y}_{1}}{\mathrm{~m}_{1}+\mathrm{m}_{2}}\right)$ ...........(i)
Here, $m_{1}=5, m_{2}=3$
$\left(\mathrm{x}_{1}, \mathrm{y}_{1}\right)=(\mathrm{a}, 0)$ and $\left(\mathrm{x}_{2}, \mathrm{y}_{2}\right)=(0, \mathrm{~b})$
Substituting the above values in the above formula, we get
$\Rightarrow \mathrm{x}=\frac{5(0)+3(\mathrm{a})}{5+3}, \mathrm{y}=\frac{5(\mathrm{~b})+3(0)}{5+3}$
$\Rightarrow-4=\frac{3 a}{8}, 3=\frac{5 b}{8}$
$\Rightarrow-32=3 a$ or $24=5 b$
$\Rightarrow \mathrm{a}=-\frac{32}{3} \mathrm{Or} \mathrm{b}=\frac{24}{5}$
We know that intercept form of the line is
$\frac{x}{a}+\frac{y}{b}=1$
Substituting the value of $a$ and $b$ in above equation, we get
$\frac{x}{-\frac{32}{3}}+\frac{y}{\frac{24}{5}}=1$
On simplification we get
$\Rightarrow-\frac{3 x}{32}+\frac{5 y}{24}=1$
Taking LCM
$\Rightarrow \frac{-72 x+160 y}{(32)(24)}=1$
On cross multiplication we get
⇒ -72x + 160y = 768
⇒ -36x + 80y = 384
⇒ 18x – 40y + 192 = 0
⇒ 9x – 20y + 96 = 0
Hence, the required equation is 9x – 20y + 96 = 0