## anonymous one year ago Use the quadratic formula to solve the equation. -2x^2+3x+5=0

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1. hartnn

Compare your quadratic equation with $$ax^2+bx+c=0$$ find $a=...?\\b=...?\\c=...?\\$ $\\ \sqrt{b^2-4ac}=...?$ then the two roots of x are: $$\huge{x_{1,2}=\frac{-b \pm \sqrt{b^2-4ac}}{2a}}$$

2. anonymous

somethings not coming up correctly :(. I tried plugging everything in.

3. hartnn

can you plz show your work?

4. anonymous

$\sqrt{3x^2-4(2x^2*5)}$

5. hartnn

okk...we can't have x in the values of a,b,c |dw:1442238245129:dw|

6. hartnn

a = -2, b =3 c = 5 got it? can you now try again ?

7. anonymous

i tried again still don't have anything :/ i'm trying to put it in the TI-30XS calculator.

8. hartnn

start by finding b^2 -4ac (3)^2 - 4(-2)(5) = ... ?

9. anonymous

49

10. hartnn

and its square root is ?

11. anonymous

7 because 7*7 is 49 :D

12. hartnn

yes! now we have the $$\sqrt{b^2 -4ac}$$ part which equals 7

13. hartnn

$$numerator = -b \pm \sqrt{b^2-4ac} = -3 \pm 7$$ so what the the 2 values of numerator? -3 +7 = ...? -3-7 = ... ?

14. anonymous

4 & -10

15. hartnn

yes, now the denominator 2a = 2(-2) = -4 so your 2 values of x are -4/4 and -10/4 simplify them!

16. ryanwhite499

Let's solve your equation step-by-step. −2x2+3x+5=0 Step 1: Factor left side of equation. (−2x+5)(x+1)=0 Step 2: Set factors equal to 0. −2x+5=0 or x+1=0 x= 5 2 or x=−1 Answer: x= 5 2 or x=−1

17. anonymous

-1 & -5/2?

18. hartnn

very good! they're correct :)

19. anonymous

Yes! thank you so much for all your help :).

20. hartnn

21. hartnn

the 2nd numerator is -10 so the 2nd value is -10/-4 = 5/2

22. hartnn

-1 and 5/2

23. hartnn

but you understand the steps, right? :)