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



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SmoothMath
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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.

patbatE21
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Set 8x = 0 and (x +4) = 0 , then the results add together

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

careoh
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Thanks! How did you get 32x?

SmoothMath
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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 = 16x16x
8x^2 +32x = 0

careoh
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So you subtracted 16x16x, do you also subtract 40x16x? If so, wouldn't that equal 24x?

SmoothMath
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Yes. Haha thank you for catching that.

SmoothMath
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Embarassing.

careoh
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haha. It's okay!

careoh
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So after, do you divide each by 8?

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

careoh
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So the answer would be 3?

SmoothMath
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Kind of almost.

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

patbatE21
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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

careoh
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So the answer is 3?

patbatE21
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yep

careoh
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That was easy! Thanks you guys!