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careoh

  • 4 years ago

How to find the SUM of the solution of the equation: 8x^2+40x=16x

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

  2. patbatE21
    • 4 years ago
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    Set 8x = 0 and (x +4) = 0 , then the results add together

  3. SmoothMath
    • 4 years ago
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    Correct, since it asks for the sum. You get two results, one from either factor.

  4. careoh
    • 4 years ago
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    Thanks! How did you get 32x?

  5. SmoothMath
    • 4 years ago
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    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
    • 4 years ago
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    So you subtracted 16x-16x, do you also subtract 40x-16x? If so, wouldn't that equal 24x?

  7. SmoothMath
    • 4 years ago
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    Yes. Haha thank you for catching that.

  8. SmoothMath
    • 4 years ago
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    Embarassing.

  9. careoh
    • 4 years ago
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    haha. It's okay!

  10. careoh
    • 4 years ago
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    So after, do you divide each by 8?

  11. SmoothMath
    • 4 years ago
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    Yeah. I get 8x^2 + 24x = 0 and you can take out a factor of 8x

  12. careoh
    • 4 years ago
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    So the answer would be 3?

  13. SmoothMath
    • 4 years ago
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    Kind of almost.

  14. SmoothMath
    • 4 years ago
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    You get a factor of (x+3) What x makes that factor 0?

  15. patbatE21
    • 4 years ago
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    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
    • 4 years ago
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    So the answer is -3?

  17. patbatE21
    • 4 years ago
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    yep

  18. careoh
    • 4 years ago
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    That was easy! Thanks you guys!

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