a: \(=\dfrac{15x^4-x^3-x^2+41x-70}{3x^2-2x+7}\)
\(=\dfrac{15x^4-10x^3+35x^2+9x^3-6x^2+21x-30x^2+20x-70}{3x^2-2x+7}\)
\(=5x^2+3x-10\)
b: \(=\dfrac{x^4-10x^2-9}{x^2-2x-3}\)
\(=\dfrac{x^4-2x^3-3x^2+2x^3-4x^2-6x-3x^2+6x+9-18}{x^2-2x-3}\)
\(=x^2+2x-3+\dfrac{-18}{x^2-2x-3}\)