Which equation shows the quadratic formula used correctly to solve [tex]$5x^2 + 3x - 4 = 0$[/tex] for [tex]x[/tex]?

A. [tex]x = \frac{-3 \pm \sqrt{(3)^2 - 4(5)(-4)}}{2(5)}[/tex]

B. [tex]x = \frac{3 \pm \sqrt{(3)^2 + 4(5)(-4)}}{2(5)}[/tex]

C. [tex]x = \frac{3 \pm \sqrt{(3)^2 - 4(5)(-4)}}{2(5)}[/tex]

D. [tex]x = \frac{-3 \pm \sqrt{(3)^2 + 4(5)(-4)}}{2(5)}[/tex]



Answer :

To solve the quadratic equation [tex]\(5x^2 + 3x - 4 = 0\)[/tex], we can use the quadratic formula:

[tex]\[ x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \][/tex]

For the given quadratic equation, the coefficients are:
- [tex]\(a = 5\)[/tex]
- [tex]\(b = 3\)[/tex]
- [tex]\(c = -4\)[/tex]

Substitute these values into the quadratic formula:

[tex]\[ x = \frac{-3 \pm \sqrt{3^2 - 4 \cdot 5 \cdot (-4)}}{2 \cdot 5} \][/tex]

Simplify inside the square root:

[tex]\[ x = \frac{-3 \pm \sqrt{9 + 80}}{10} \][/tex]
[tex]\[ x = \frac{-3 \pm \sqrt{89}}{10} \][/tex]

Therefore, the correct formula being used is:

[tex]\[ x = \frac{-3 \pm \sqrt{(3)^2 - 4(5)(-4)}}{2(5)} \][/tex]

So, the correct answer from the given options is:

[tex]\[ x = \frac{-3 \pm \sqrt{(3)^2 - 4(5)(-4)}}{2(5)} \][/tex]