1. 2x(1 - x) - (x - 1)=-(x-1)(2x+1)=-2x^2+x+1
2.x^2 - 8x + 16=(x-4)^2
3.(a - b)(a + b)=a^2-b^2
4.(a - b)^2 - (a + b)^2=[(a-b)+(a+b)][(a-b)-(a+b)]=2a*(-2b)=-4ab
5.2(m + n) /3 - 1/5m=(10m+10n-3m)/15=(7m+10n)/15=7m/15+2n/3
6.1/5x^2 - x(x - 8)=x^2/5-x^2+8x=-4/5x^2+8x