Solve \(\displaystyle \frac{3}{x} - \frac{x}{x + 6} = \frac{18}{x^2 + 6x}\)
common denominator is x (x+6) = x^2 +6x
[3 (x+6) - x(x) ] / x^2+6 = 18 / x^2 + 6 equate the numerators
3x+18 - x^2 = 18
3x = x^2
+-3 = x (throw out -3)