The quadratic equation whose roots are the $\mathrm{x}$ and yintercepts of the line passing through (1,1)…

The quadratic equation whose roots are the $\mathrm{x}$ and yintercepts of the line passing through (1,1) and making a triangle of area $\mathrm{A}$ with the co-ordinate axes is
  1. $x^{2}+A x+2 A=0$
  2. $x^{2}-2 A x+2 A=0$
  3. $x^{2}-A x+2 A=0$
  4. None of these

Solution

Equation of the line making intercepts a and $b$ on the axes is $\frac{x}{a}+\frac{y}{b}=1$ Since, it passes through (1,1) $\Rightarrow \frac{1}{\mathrm{a}}+\frac{1}{\mathrm{~b}}=1$ Also the area of the triangle formed by the line and the axes is $\mathrm{A}$. $\therefore \frac{1}{2} \mathrm{ab}=\mathrm{A} \Rightarrow \mathrm{ab}=2 \mathrm{~A}$ From eqs. (i) and (ii), we get, $a+b=2 A$ Hence, a and b are the roots of the eq. $x^{2}-(a+b) x+a b=0 \Rightarrow x^{2}-2 A x+2 A=0$

Asked in: BITSAT 2013

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