Question

Use the quadratic formula to solve x2 + 7x + 8 = 0. Estimate irrational solutions to the nearest tenth.

A.
{–12, 5}

B.
{–11.1, –2.9}

C.
{–5.6, –1.4}

D.
{–3.9, 12.1}

Answer 1

hint:
\[\Large x = \frac{{ - 7 \pm \sqrt {{7^2} - 4 \times 1 \times 8} }}{{2 \times 7}}\]

Answer 2

For quadratic formulas you have the basic form
\[ax^2+bx+c=0\]
And than you should determine your determinator which is \[b^2-4ac\]
And then your solutions are \[\frac{ -b \pm \sqrt{determinator} }{ 2a }\]

Answer 3

i need help on the solving

Answer 4

i already had help at the begenning but, the user left off at the following part

Answer 5

@Michele_Laino

Answer 6

that's right! So we have:
\[\begin{gathered}
{x_1} = \frac{{ - 7 + 4.12}}{{14}} = - 0.21 \hfill \\
\hfill \\
{x_2} = \frac{{ - 7 - 4.12}}{{14}} = - 0.79 \hfill \\
\end{gathered} \]

Answer 7

oops.. I have made an error, here are the right formulas:

Answer 8

\[\Large \begin{gathered}
x = \frac{{ - 7 \pm \sqrt {{7^2} - 4 \times 1 \times 8} }}{2} \hfill \\
{x_1} = \frac{{ - 7 + 4.12}}{2} = - 1.44 \hfill \\
\hfill \\
{x_2} = \frac{{ - 7 - 4.12}}{2} = - 5.56 \hfill \\
\end{gathered} \]