Question

If one root of the equation x${}^2$ + px + 12 = 0 is 4 while the equation x${}^2$ + px + q = 0 has equal roots, the value of q is

• A. 49/4
• B. 4/49
• C. 4
• D. None of these

Answer 1

Answer: (A)

49/4

One root of the equation $x^2+px+12=0$ is $4$

$\Rightarrow 16+4p+12=0$

$\therefore p=-7$

as $x^2+px+q=0$ has equal roots.

$b^2=4ac$ $\Rightarrow p^2=4q$

$\therefore q=\frac{49}{4}$

Hence, option A.