a/ $\left(x-2\right)^2\left(2x-5\right)\left(2x-3\right)-5$
= $\left(x^2-2. 2x+2^2\right)\left[2x\left(2x-3\right)-5\left(2x-3\right)\right]-5$
= $\left(x^2-4x+4\right)\left(4x^2-6x-10x+15\right)-5$
= $\left(x^2-4x+4\right)\left(4x^2-16x+15\right)-5$
b/ $\left(3x-2\right)^2\left(6x-5\right)\left(6x-3\right)-5$
= $\left[\left(3x\right)^2-2.3x.2+2^2\right]\left[6x\left(6x-3\right)-5\left(6x-3\right)\right]-5$
= $\left(9x^2-12x+4\right)\left(36x^2-18x-30x+15\right)-5$
= $\left(9x^2-12x+4\right)\left(36x^2-48x+15\right)-5$
