a: \(=\dfrac{2x^3+x^2-6x^2-3x+2x+1}{2x+1}=x^2-3x+1\)
b: \(=\dfrac{x^3+2x^2-2x^2-4x+2x+4}{x+2}=x^2-2x+2\)
c: \(=\dfrac{6x^3-9x^2-10x^2+15x+8x-12}{2x-3}\)
\(=3x^2-5x+4\)
d: \(=\dfrac{\left(x^2-1\right)\left(x^2+1\right)-2x\left(x^2-1\right)}{x^2-1}=x^2-2x+1\)
g: \(=\dfrac{x^3+2x^2-4x^2-8x+3x+6}{x+2}=x^2-4x+3\)
h: \(=\dfrac{x^3+x^2-3x^2-3x+8x+8}{x+1}=x^2-3x+8\)