(a-5)(a-3)= a^2 -3a+5a+15=a^2 +2a+15
(5x+4)2x-1)=10x^2-5x+8x-4=10x^2+3x-4
(3p+2c)(2p-4c)=6p^2-12pc+4pc-8c^2=6p^2-8pc-8c^2
(b-2)(b^2-2b-3)=2b^3-2b^2-3b-2b^2+4b+6=2b^3+4b+6
0.5x(4x^2-1)(5x^2+2)=0.5x(20x^4+8x^2-5x^2-2)=0.5x(20x^4+3x^2 -2)=10x^5+1.5x^3-x