JEE MAIN - Mathematics (2023 - 10th April Evening Shift - No. 18)
Let the equations of two adjacent sides of a parallelogram $$\mathrm{ABCD}$$ be $$2 x-3 y=-23$$ and $$5 x+4 y=23$$. If the equation of its one diagonal $$\mathrm{AC}$$ is $$3 x+7 y=23$$ and the distance of A from the other diagonal is $$\mathrm{d}$$, then $$50 \mathrm{~d}^{2}$$ is equal to ____________.
Answer
529
Explanation
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We have, $A B C D$ is a parallelogram
Let equation of $A B$ be $2 x-3 y=-23 \ldots$ (i)
and equation of $B C$ be $5 x+4 y=23\ldots$ (ii)
Equation of $A C$ is $3 x+7 y=23 \ldots$ (iii)
Solving Eqs. (i) and (ii), we get
$x=-1$, and $y=7$
$\therefore$ Co-ordinate of $B$ is $(-1,7)$
On solving Eqs. (ii) and (iii), we get
$$ x=3, y=2 $$
$\therefore$ Co-ordinate of $C$ is $(3,2)$
On solving Eqs. (i) and (iii), we get $x=-4$ and $y=5$
$\therefore$ Co-ordinate of $A$ is $(-4,5)$.
Let $E$ be the intersection point of diagonal co-ordinate of
$E$ is $\left(\frac{-4+3}{2}, \frac{5+2}{2}\right)$ or $\left(-\frac{1}{2}, \frac{7}{2}\right)$
$\because E$ is mid-point of $A C$
$$ \begin{aligned} & \text { Equation of } B D \text { is } y-7=\left(\frac{7-\frac{7}{2}}{-1+\frac{1}{2}}\right)(x+1) \\\\ & \Rightarrow 7 x+y=0 \end{aligned} $$
Distance of $A$ from diagonal $B D=\frac{|7 \times(-4)+5|}{\sqrt{7^2+1^2}}$
$$ \therefore d=\frac{23}{\sqrt{50}} $$
Hence, $50 d^2=(23)^2=529$
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