Question

If the roots of the quadratic equation $3x^2-12x+m=0$ are equal, then the value of $m$ will be:

• A. $4$
• B. $7$
• C. $9$
• D. $12$

Answer 1

Answer: (D)

$12$

If the roots of the given quadratic equation $a{x}^2+bx+c=0$ are equal then

$\Rightarrow b^2-4ac=0$

Comparing $3x^2-12x+m=0$ with $a{x}^2+bx+c=0$ we get, $a=3,b=12$ and $c=m$

$\Rightarrow {12}^2-(4\times 3\times m)=0\Rightarrow 12(12-m)=0$

$\Rightarrow 12-m=0$

$\Rightarrow m=12$