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# One more algebraic thing

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If $\frac{x-y}{x+y} = \frac52,$ find $\frac xy.$

Aug 18, 2021

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2x - 2y = 5x + 5y

-3x = 7y

x = -(7/3)y

so x/y = -7/3.

Check: we can actually solve this equation : x - y = 5, and x + y = 2. Add the 2 equations, and get 2x = 7, so x = 3.5, so y = -1.5. x / y = 3.5 / -1.5 = -7/3.

Aug 19, 2021