Find the slope of f(x) = (-2x) /(√(1 - x²) ) .
a) (x² + 2) /(1 - x²) ³/2)
b) (x² - 2) /(1 - x²) ³/2)
c) (-x² + 2) /(1 - x²) ³/2)
d) (-x² - 2) /(1 - x²) ³/2)