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}

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}

campbell_st · Answer

do you know the general quadratic formula...?

campbell_st · Answer

ok.... so you don't know the formula.... or you just want answers to your homework quiz...?

xmoses1 · Answer

If you know the formula then the question is relatively easy ^^

anonymous · Answer

sorry i didnt read that i have the  math book in front of me but im not understanding it

campbell_st · Answer

ok... so the book would say something like... for a quadratic equation 

$$ax^2 + bx + c = 0$$

the general quadratic formula is 

$$x=\frac{-b \pm \sqrt{b^2 - 4 \times a \times c}}{2 \times a}$$

in your question a = 1, b = 7 and c = 8

just substitute them.... then calculate the 2 answers...

campbell_st · Answer

well when you substitute you get

$$x =\frac{ -7 \pm \sqrt{49 - 32}}{2} = \frac{ -7 \pm \sqrt{17}}{2}$$

so the 2 solutions are 

$$x = \frac{-7 + \sqrt{17}}{2}.....and.......x = \frac{-7-\sqrt{17}}{2}$$

that may help you find the solutions...

anonymous · Answer

i actually did all that but i divided them into eachoter 17 and 2 thats how i got 8.5

campbell_st · Answer

well there is an answer is the list that's really close to my mental arithmetic solutions