Find the negative root of $$3x^2+12x-15=0.$$​​

Correct option is C

Given : 

​Quadratic Equations :$$3x ^2+12x-15=0$$

Formula used  : ​

Standard form of equation :$$ax^2+bx+c=0$$ 

$$x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}$$

Solution :   

From the equation:

Here,$a=3$,$b=12$, and$c=-15$.​

$$x = \frac{-12 \pm \sqrt{12^2 - 4\times3\times(-15)}}{2\times 3}$$

$$x = \frac{-12 \pm \sqrt{144+180}}{6}$$

 $$x = \frac{-12\pm\sqrt {324}}{6}$$

 $$x = \frac{-12 \pm 18}{6}$$

Roots are :

 $$x=\frac{-12+18}{6}=\frac{6}{6}=1$$  

 $$x=\frac{-12-18}{6}=\frac{-30}{6}=-5$$  

The negative root is $x=-5$.