andriod09 Group Title Need help on Quadratic equations please! The equation is on the comments. one year ago one year ago

1. andriod09 Group Title

$4x^{2}+9x=0$ i know that the answer is: $x=\frac{ -9\pm \sqrt{81-4(4)(2)} }{ 8 }$

2. gezimbasha Group Title

Much easier to solve your problem would be to factor out an x,$x(4x+9)=0$now you have two solutions,$x=0$and$4x+9=0$$4x=-9$$x=-\frac{9}{4}$and you get

3. imron07 Group Title

The equation is correct. But you put innocent "2" instead of "0" for c.

4. andriod09 Group Title

huh? the thing messed up, give me a sec

5. gezimbasha Group Title

Well, then you can do the following:$x_{1/2}=\frac{-9 \pm \sqrt{9^2-4*4*0}}{2*4}$simplifying that you get,$x_{1/2}=\frac{ -9 \pm 9 }{ 8 }$Compute the rest

6. andriod09 Group Title

I have to use: $ax^{2}+bx+c=0$ and i have to use: $x=\frac{ -b\pm \sqrt{b^{2}-4ac} }{ 2a }$

7. gezimbasha Group Title

Yes.. that is what I have used. Just make c=0, and you will get the same result as I have.

8. andriod09 Group Title

but c = 2... thats what the answer says.

9. gezimbasha Group Title

Well then you have given us a wrong problem$4x^2+9x=0$does not have a c in it..

10. andriod09 Group Title

my bad... /facepalm its: $4x^{2}+9x+2=0$

11. andriod09 Group Title

@gezimbasha

12. gezimbasha Group Title

Hehe, no worries. Now you have to use the formula you input$x_{1/2}=\frac{-9 \pm \sqrt{9^2-4*4*2}}{2*4}$compute the values inside the square root first$x_{1/2}=\frac{-9 \pm \sqrt{81- 32}}{8}$and complete calculation$x_{1/2}=\frac{-9 \pm 7}{8}$ and you get,$x_1= -2$$x_2=-\frac{1}{4}$

13. andriod09 Group Title

where did you get $x _{1/2}$

14. gezimbasha Group Title

That just means that there are two solutions we will get from the equation. Its just mathematical notation. I am used to writing it like that. Don't worry, you can write just x, it will be fine.

15. andriod09 Group Title

im only in high school. :/ :L

16. gezimbasha Group Title

Yeah I figured. The quadratic equations are studied extensively in high school. You're doing good tho. Might want to reconsider your profile picture heh ;)

17. andriod09 Group Title

it says i don't hate math. open my profile and look at the white! everyone says that. lol do you not see the white scribble on the $^{don't}$ I hate math

18. gezimbasha Group Title

Oh.. then I owe you an apology. XD.

19. andriod09 Group Title

Its okay. I need to make it bigger anyway. lol. Thanks tho.

20. gezimbasha Group Title

You're welcome man. Anytime!

21. andriod09 Group Title

I gave you a medal. dont for get to give one back~ ;)

22. gezimbasha Group Title

Hey, my bad, my first day over here.

23. andriod09 Group Title

what do you mean?

24. gezimbasha Group Title

This is my first day in open study, so I'm still getting used to the medals and stuff.

25. andriod09 Group Title

how would i set up: $3x^{2}+11x+5=0$ and oh. i didn't know

26. gezimbasha Group Title

Same principle, replace a=3, b=11, and c=5.

27. andriod09 Group Title

i mean in the fraction form