b/ (2x - 1)2 - 2x (1 +2x)
= 4x2 - 4x + 1 - 2x - 4x2
= -6x + 1
a, \(\dfrac{6}{x^2-9}\) + \(\dfrac{5}{x-3}\) - \(\dfrac{2}{x+3}\)
= \(\dfrac{6}{\left(x-3\right)\left(x+3\right)}\) + \(\dfrac{5\left(x+3\right)}{\left(x-3\right)\left(x+3\right)}\) - \(\dfrac{2\left(x-3\right)}{\left(x+3\right)\left(x-3\right)}\)
= \(\dfrac{6+5x+15-2x+6}{\left(x-3\right)\left(x+3\right)}\) = \(\dfrac{27+3x}{\left(x+3\right)\left(x-3\right)}\)