2/5x - x/4 = 4

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- Dec 11th 2007, 04:39 AMlovely08find the solution set of the equation
2/5x - x/4 = 4

- Dec 11th 2007, 05:00 AMcolby2152
$\displaystyle \frac{2}{5x} - \frac{x}{4} = 4$

Find a common denominator. Easy way to do that is multiply all denominators with each other: 5x*4 = 20x. Now, multiply the entire equality by 20x (same as multiplying each term by 20x).

$\displaystyle \frac{40x}{5x}- \frac{20x^2}{4} = 80x$

Simplify it...

$\displaystyle 8-5x^2=80x$

$\displaystyle 5x^2+80x-8$

Quadratic formula will solve it...

$\displaystyle x = \frac{-80 \pm \sqrt{80^2 - 4(-8)(5)}}{10}$

$\displaystyle x = \frac{-80 \pm -80.994}{10}$

$\displaystyle x = -8 \pm - 8.0994$

$\displaystyle x = 0.0994, -16.0994$