## careoh 3 years ago How to find the SUM of the solution of the equation: 8x^2+40x=16x

1. SmoothMath

8x^2 + 40x = 16x (-16x) 8x^2 + 32x = 0 8x(x + 4) = 0 I'll let you take it from here.

2. patbatE21

Set 8x = 0 and (x +4) = 0 , then the results add together

3. SmoothMath

Correct, since it asks for the sum. You get two results, one from either factor.

4. careoh

Thanks! How did you get 32x?

5. SmoothMath

By subtracting 16x from both sides and then grouping like terms. Like this: 8x^2 +40x = 16x 8x^2 +40x -16x = 16x-16x 8x^2 +32x = 0

6. careoh

So you subtracted 16x-16x, do you also subtract 40x-16x? If so, wouldn't that equal 24x?

7. SmoothMath

Yes. Haha thank you for catching that.

8. SmoothMath

Embarassing.

9. careoh

haha. It's okay!

10. careoh

So after, do you divide each by 8?

11. SmoothMath

Yeah. I get 8x^2 + 24x = 0 and you can take out a factor of 8x

12. careoh

So the answer would be 3?

13. SmoothMath

Kind of almost.

14. SmoothMath

You get a factor of (x+3) What x makes that factor 0?

15. patbatE21

you can factor out as 4x(2x+6) then set both to zero and you should end up with x= 0 & x = -3 and add them

16. careoh

17. patbatE21

yep

18. careoh

That was easy! Thanks you guys!