a: Ta có: A=(5x-2)(x+1)-(x-3)(5x+1)-17(x+3)
\(=5x^2+5x-2x-2-\left(5x^2+x-15x-3\right)-17x-51\)
\(=5x^2-14x-53-\left(5x^2-14x-3\right)\)
\(=5x^2-14x-53-5x^2+14x+3\)
=-53+3
=-50
b: \(B=\left(6x-5\right)\left(x+8\right)-\left(3x-1\right)\left(2x+3\right)-9\left(4x-3\right)\)
\(=6x^2+48x-5x-40-\left(6x^2+9x-2x-3\right)-36x+27\)
\(=6x^2+7x-13-6x^2-7x+3\)
=-13+3
=-10