Question

solve $0 = 4x^2 + 12x + 9$
select the equation that shows the correct substitution of $a$, $b$, and $c$ in the quadratic formula.
$\circ$ $x = \frac{12 \pm \sqrt{12^2 - 4(4)(9)}}{2(4)}$
$\circ$ $x = \frac{-12 \pm \sqrt{12^2 + 4(4)(9)}}{2(4)}$
$\circ$ $x = \frac{-12 \pm \sqrt{12^2 - 4(4)(9)}}{2(4)}$

Explanation:

Step1: Identify quadratic coefficients

For $ax^2+bx+c=0$, here $a=4$, $b=12$, $c=9$.

Step2: Recall quadratic formula

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

Step3: Substitute values into formula

Substitute $a=4$, $b=12$, $c=9$:
$x=\frac{-12\pm\sqrt{12^2-4(4)(9)}}{2(4)}$

Answer:

$\boldsymbol{x=\frac{-12\pm\sqrt{12^2-4(4)(9)}}{2(4)}}$ (the third option)