Find equation of the line passing through the point (2, 2) and
Find equation of the line passing through the point (2, 2) and cutting off intercepts on the axes whose sum is 9.
The equation of a line in the intercept form is
$\frac{x}{a}+\frac{y}{b}=1$ (i)
Here, a and b are the intercepts on x and y axes respectively.
It is given thata $+b=9 \Rightarrow b=9-a \ldots$ (ii)
From equations (i) and (ii), we obtain
$\frac{x}{a}+\frac{y}{9-a}=1$ ...(iii)
It is given that the line passes through point $(2,2)$. Therefore, equation (iii) reduces to
$\frac{2}{a}+\frac{2}{9-a}=1$
$\Rightarrow 2\left(\frac{1}{a}+\frac{1}{9-a}\right)=1$
$\Rightarrow 2\left(\frac{9-a+a}{a(9-a)}\right)=1$
$\Rightarrow \frac{18}{9 a-a^{2}}=1$
$\Rightarrow 18=9 a-a^{2}$
$\Rightarrow a^{2}-9 a+18=0$
$\Rightarrow a^{2}-6 a-3 a+18=0$
$\Rightarrow a(a-6)-3(a-6)=0$
$\Rightarrow(a-6)(a-3)=0$
$\Rightarrow a=6$ or $a=3$
If $a=6$ and $b=9-6=3$, then the equation of the line is
$\frac{x}{6}+\frac{y}{3}=1 \Rightarrow x+2 y-6=0$
If $a=3$ and $b=9-3=6$, then the equation of the line is
$\frac{x}{3}+\frac{y}{6}=1 \Rightarrow 2 x+y-6=0$