Q. A value of $k$ for which the quadratic equation $x^{2} - 2x(l + 3k) + 7(2k + 3) = 0$ has equal roots, is
A) 1
B) 2
C) 3
D) 4
Explanation
(b)
Given equation is
$x^{2} - 2x(1 + 3k) + 7(2k + 3) = 0$
For equal roots, discriminant=0
$\therefore\ \ \ 4(1 + 3k)^{2} = 4 \times 7(2k + 3$
$\Rightarrow \ \ 9k^{2} - 8k - 20 = 0\ \Rightarrow k = 2,\ \frac{- 10}{9}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.