a. \(\dfrac{-5}{4}\) x4 . \(\dfrac{8}{15}\) x = \(\dfrac{-40}{60}\) x5 = \(\dfrac{-2}{3}\) x5
b. -2x\(\left(\dfrac{3}{4}x^2-x+\dfrac{1}{2}\right)\) = -\(\dfrac{-3}{2}\) x3 + 2x3 - x
c. \(x\left(x-\dfrac{1}{2}\right)\) - (x - 2)(x + 3)
= x2 - \(\dfrac{1}{2}\) x - x2 - 3x - 2x - 6