Answer:
[tex]D. \ \ x=\frac{-b\pm \sqrt{b^{2}-4ac} }{2a}[/tex]
Step-by-step explanation:
ax² + bx + c = 0
[tex]a\left( x^{2}+\frac{b}{a} x+\frac{c}{a} \right) =0[/tex]
[tex]a\left( \left( x+\frac{b}{2a} \right)^{2} -\frac{b^{2}}{4a^2}+\frac{c}{a} \right) =0[/tex]
[tex]a\left( \left( x+\frac{b}{2a} \right)^{2} -\frac{b^{2}-4ac}{4a^2}\right) =0[/tex]
[tex]a\left( x+\frac{b}{2a} \right)^{2} -\frac{b^{2}-4ac}{4a}=0[/tex]
[tex]a\left( x+\frac{b}{2a} \right)^{2} =\frac{b^{2}-4ac}{4a}[/tex]
[tex]\left( x+\frac{b}{2a} \right)^{2} =\frac{b^{2}-4ac}{4a^2}[/tex]
[tex]x+\frac{b}{2a} =\frac{\pm \sqrt{b^{2}-4ac} }{2a}[/tex]
[tex]x=\frac{-b\pm \sqrt{b^{2}-4ac} }{2a}[/tex]
