## anonymous one year ago 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}

1. Michele_Laino

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

2. anonymous

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 $\frac{ -b \pm \sqrt{determinator} }{ 2a }$

3. anonymous

i need help on the solving |dw:1433008252754:dw|

4. anonymous

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

5. anonymous

@Michele_Laino

6. Michele_Laino

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

7. Michele_Laino

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

8. Michele_Laino

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

9. anonymous

okay!

10. anonymous

the answer would be c?

11. anonymous

@Michele_Laino

12. Michele_Laino

yes! that's right! Sorry for my previous error