1)12ab-3bˇ2=3b(4a-b)
ac+bc-2a-2b=c(a+b)-2.(a+b)=(a+b)(c-2)
2)4xˇ3-x=0, x(4xˇ2-1)=0, x(2x+1)(2x-1)=0
x1=0, x2=-1/2, x3=1/2
3)(6-6x)/(xˇ2-2x+1)=6(1-x)/(x-1)(x-1)=
= -6(x-1)/(x-1)(x-1)=-6/(x-1)
4)507ˇ2-493ˇ2=(507+493)(507-493)=1000.14=14000
5)2a(a+b-c)-2b(a-b-c)+2c(a-b+c)=
=2aˇ2+2ab-2ac-2ab+2bˇ2+2bc+2ac-2bc+2cˇ2=
=2aˇ2+2bˇ2+2cˇ2=2.(aˇ2+bˇ2+cˇ2)