If points $( a,\ 0),\ ( 0,\ b)$ and $( x,\ y)$ are collinear, prove that $\frac{x}{a}+\frac{y}{b}=1$.


Given: Points $( a,\ 0),\ ( 0,\ b)$ and $( x,\ y)$ are collinear.

To do: To prove that $\frac{x}{a}+\frac{y}{b}=1$.

Solution:

Given that three points are collinear, $( a,\ 0),\ ( 0,\ b)$ and $( x,\ y)$.

$\because$ The points are collinear, area of triangle formed by these points should be equal to $0$.

$\frac{1}{2}[x_1( y_2-y_3)+x_2( y_3-y_1)+x_3( y_1-y_2)]=0$

$\frac{1}{2}[a[b-y]+0[x-0]+x(0-b)]=0$

$\Rightarrow ab-ay-bx=0$

$\Rightarrow ay+bx=ab$

$\Rightarrow \frac{ay}{ab}+\frac{bx}{ab}=\frac{ab}{ab}$         [On dividing both sides by $ab$]

$\Rightarrow \frac{y}{b}+\frac{x}{a}=1$

Hence proved.

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Updated on: 10-Oct-2022

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