Question

which of the choices represents a solution of the equation?
$4x^2 - 9 = 0$
click on the correct answer.
$\frac{sqrt{-4(4)(-9)}}{2(4)}$
$\frac{9 + sqrt{81 - 4(4)(-9)}}{2(4)}$
$\frac{9 + sqrt{81}}{2(4)}$

Explanation:

Step1: Recall quadratic formula

For $ax^2+bx+c=0$, $x=\frac{-b\pm\sqrt{b^2-4ac}}{2a}$

Step2: Identify a, b, c

$a=4$, $b=0$, $c=-9$

Step3: Substitute into formula

$x=\frac{0\pm\sqrt{0^2-4(4)(-9)}}{2(4)}=\frac{\sqrt{-4(4)(-9)}}{2(4)}$

Answer:

$\frac{\sqrt{-4(4)(-9)}}{2(4)}$