The graph $x y = 1$ is reflected in $y = 2 x$ to give the graph of the curve $12 x^{2} + r x y + s y^{2} + t = 0$ , then the number of prime factors of $\frac{r s t}{20} = ........$

see full answer

Your Exam Success, Personally Taken Care Of

1:1 expert mentors customize learning to your strength and weaknesses – so you score higher in school , IIT JEE and NEET entrance exams.

An Intiative by Sri Chaitanya

answer is A.

(Unlock A.I Detailed Solution for FREE)

Best Courses for You

JEE

NEET

Foundation JEE

Foundation NEET

CBSE

Detailed Solution

Let the image of $A (α, β)$ about $y = 2 x b e B (a, b)$ mid point of $\bar{A B} = (\frac{α + a}{2}, \frac{β + b}{2})$ lie on y - 2x = 0
$\Rightarrow β + b = 2 α + 2 a ............ (1)$ and slope of

$\bar{A B} = \frac{- 1}{2} \Rightarrow \frac{β - b}{α - b} = \frac{- 1}{2} \Rightarrow β - b = \frac{- 1}{2} a + \frac{a}{2} ........... (2)$

(1) and (2) $\Rightarrow 2 b = \frac{5}{2} a + \frac{3}{2} α \Rightarrow α = \frac{4 b - 3 a}{5} \Rightarrow B = \frac{8 b - 6 a}{5} + 2 a - b = \frac{3 b + 49}{5}$
(2) $(α, β)$ lie on xy = 1 $\Rightarrow \frac{4 b - 3 a}{5} . \frac{3 b + 4 a}{5} = 1$
$\begin{array}{l} \Rightarrow 12 b^{2} + 7 a b - 12 a^{2} = 25 \\ \Rightarrow 12 x^{2} - 7 x y - 12 y^{2} + 25 = 0 \\ \Rightarrow r = - 7, s = - 12, t = 25 \end{array}$