1.а) (2а-1)^2=4а^2-4а+1;
б) (х+3у)^2=х^2+6ху+9у^2;
в) (1/5 х-у)(1/5 х+у)=1/25 х^2-у^2;
2.а) (с-2)(с+3)-(с-1)^2=с^2+3с-2с-6-с^2+2с-1=
=3с-7;
б) 2(а+с)^2 -6ас=2а^2+4ас+2с^2-6ас=
=2а^2-2ас+2с^2;
в) (р-3)(р^2+3р+9)-р^3=
=р^3-27-р^3=-27;
3. (12а^3-3а^2в)÷3а=4а^2-ав;
а=-2; в=10;
4×(-2)^2-(-2)×10=16+20=36;
4.(2х+3)(3х+1)+(5х+2)(2х+5)=(4х-1)^2;
6х^2+2х+9х+3+10х^2+25х+4х+10=
=16х^2-8х+1;
38х=-12;
х=-12/38=-6/19.