Question

If the roots of the equation $9x^2+(k-2)x-2=0$ are equal in magnitude but opposite in sign, then $k=............$

• A. $0$
• B. $8$
• C. $2$
• D. $10$

Answer 1

Answer: (C)

$2$

let the one root of the given quadratic equation be $a$.

So, the other root will be $-a$

We know that for a general quadratic equation $a{x}^2+bx+c$,

Sum of roots $=\frac{-b}{a}$

Therefore in the given given quadratic equation,

Sum of roots $=a+(-a)=0$

$\begin{array}{c}\frac{-\left(k-2\right)}{9}=0\\ k-2=0\\ k=2\end{array}$

Thus Option C is correct.