## Baldwin777 2 years ago 2x^2+4x=16 x=?

1. pottersheep

Rearrange it to become 2x^2+4x - 16 = 0 Then plug it into the formula or factor it

2. pottersheep

You can factor out a 2, see where that gets you..

3. pottersheep

Do you get it?

4. Baldwin777

no,I don't

5. pottersheep

it becomes 2(x^2 + 2x - 8) = 0 when you factor it

6. pottersheep

Can you factor x^2 + 2x - 8 ?

7. Baldwin777

okay let me try this

8. Baldwin777

it would be (x+4)(x-2) right?

9. pottersheep

Do you know the formula? The quadratic formula?

10. Baldwin777

Yes and no, I forgot the steps

11. pottersheep

Nice you factored it right

12. Baldwin777

So then I would plug the x+4 and x-2 into the equation right,? it would be 2(4)^2+4(-2)=16??

13. pottersheep

So 2(x^2 + 2x - 8) = 0 2 (x - 2 ) ( x + 4 ) = 0 NOW, you know how anything times zero = 0? You have to make at least one of the brackets = 0 to get zero as an overall answer. So what can we put as x to make the brackets zero? There is x in two places so there are 2 answers

14. pottersheep

To find the answers, factoring is one way. The formula is another. Yo chose to factor so you dont need to use the formula anymore

15. Baldwin777

2x-2=0 and 2x+4=0

16. pottersheep

You just have to make the brackets = 0, don't put in the two! See we got 2 (x - 2 ) ( x + 4 ) = 0 So, one bracket is (x-2) . We want to make this = 0 x-2 = 0 x = 2 !!! One of the answers.. Next bracket (x+4) Make it equal to zero. x+4 = 0 x= -4 So the answer is x = -4 or x = 2

17. Baldwin777

oh wow, that was really simple, Now I under stand

18. pottersheep

Yay!! :)

19. Baldwin777

Thank u

20. pottersheep

you're welcome

Find more explanations on OpenStudy