(1-2b)(1-5b+b^2)+(2b-1)(1-6b+b^2)= =(1-5b+b^2-2b+10b^2-2b^3)+(2b-12b^2+2b^3-1+6b-b^2)= =(1-7b+11b^2-2b^3)+(-1+8b-13b^2+2b^3)= =b-2b^2= =b(1-2b)