Simple algebra problem
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Simple algebra problem

[From: ] [author: ] [Date: 12-08-09] [Hit: ]
......
How do I algebraically solve this problem?

200/(r+10) = 200/r -1

I know the answer is obviously 40 from looking at it but how do i manipulate this equation to give me this?

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200 / (r + 10) = 200 / r − 1

Multiply by (r + 10) on both sides:

200 = (200 / r − 1)(r + 10)

Multiply by r on both sides:

200r = (200 − r)(r + 10)

Multiply out:

200r = − r^2 + 190r + 2000

Rearrange to standard quadratic form:

r^2 + 10r − 2000 = 0

Factor:

(r − 40)(r + 50) = 0

Solutions:

[r = 40] or [r = − 50]
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