Q. Suppose that two persons $A$ and $B$ solve the equation $x^{2} + ax + b = 0$. While solving $A$ commits a mistake in the coefficient of $x$ was taken as 15 in place of $- 9$ and finds the roots as $- 7$ and $- 2$. Then the equation is
A) $x^{2} + 9x + 14 = 0$
B) $x^{2} - 9x + 14 = 0$
C) $x^{2} + 9x - 14 = 0$
D) $x^{2} - 9x - 14 = 0$
Explanation
(b)
Let the incorrect equation is
$x^{2} + 15x + b = 0$
Since, roots are -7 and -2
$\therefore$ Product of roots, $b = 14$
So, correct equation is $x^{2} - 9x + 14 = 0$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.