a)(2x-3)(4x+1)=2x*4x+2x-3*4x-3=8x²+2x-3*4x-3=8x²+2x-12x-3=8x²-10x-3
б)(3x-y)(2y-7x)=3x*2y-3x*7x-y*2y-y(-7x)=6xy-21x²-2y²+7xy=13xy-21x²-2y²
в)a(a+4)-(a-2)(a+6)=a²+4a-(a²+4a-12)=a²+4a-a²-4a+12=12
г)(1-3p)(9p²+3p+1)=1(9p²+3p+1)-3p(9p²+3p+1)=9p²+3p+1-27p³-9p²-3p=1-27p³