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Mathematics 16 Online
OpenStudy (shaleiah):

Please help (quadratic formula)

OpenStudy (shaleiah):

@Mimi_x3

OpenStudy (mathstudent55):

Can you find a copy of the quadratic formula and post it?

OpenStudy (shaleiah):

\[-b \pm \sqrt{b^2-4ac}/2a\]

OpenStudy (mathstudent55):

The 2a denominator is below the entire expression before it.

OpenStudy (mathstudent55):

Now simply use 5 for a, 3 for b, and -2 for c in the quadratic formula. Then simplify the expression.

OpenStudy (shaleiah):

2/5

OpenStudy (mathstudent55):

\(k = \dfrac{-\color{red}{b} \pm \sqrt{\color{red}{b}^2 - 4\color{green}{a}\color{purple}{c}}}{2\color{green}{a}}\) \(\color{green}{a = 5}\) \(\color{red}{b = 3}\) \(\color{purple}{c = -2}\) \(k = \dfrac{-\color{red}{3} \pm \sqrt{\color{red}{3}^2 - 4(\color{green}{5})(\color{purple}{-2})}}{2(\color{green}{5})}\)

OpenStudy (mathstudent55):

\(k = \dfrac{-3 \pm \sqrt{9 - (-40)}}{10}\) \(k = \dfrac{-3 \pm \sqrt{49}}{10}\) \(k = \dfrac{-3 \pm 7}{10}\) Did you get to this point?

OpenStudy (shaleiah):

yes

OpenStudy (mathstudent55):

Good. Now you need to know what to do with the \(\pm\).

OpenStudy (mathstudent55):

After you simplify the solution as much as possible while you still have the \(\pm\), you need to turn it into two equations, one for the + case, and one for the - case. The two equations are separated by the word "or."

OpenStudy (mathstudent55):

\(k = \dfrac{-3 \pm 7}{10}\) \(k = \dfrac{-3 + 7}{10}\) or \(k = \dfrac{-3 -7}{10}\) Now you solve each equation above and always kep the word "or" in between them.

OpenStudy (shaleiah):

\[\frac{ -3-7 }{ 10 }=-1\]

OpenStudy (shaleiah):

\[\frac{ -3+7 }{ 10 }=\frac{ 2 }{ 5 }\]

OpenStudy (mathstudent55):

\(k = \dfrac{-3 + 7}{10}\) or \(k = \dfrac{-3 - 7}{10}\) \(k = \dfrac{4}{10}\) or \(k = \dfrac{-10}{10}\) \(k = \dfrac{2}{5}\) or \(k = -1\)

OpenStudy (mathstudent55):

You are correct. Those two solutions are correct.

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