№1
(3x-1)²-8(x+1)²=(x+2)(x-2)
9x²-6x+1-8x²-16x-8=x²-4
x²-22x-7=x²-4
-22x-3=0
22x=-3
x=-3/22
№2
(2a-b)(a+b-c)-(a+2b)(a-b+c)+3c(a+b)=
=2a²+2ab-2ac-ab-b²+bc-(a²-
-ab+ac+2ab-2b²+2bc)+3ac+3bc=
=2a²-a²+2ab-ab-ab-2ac-
-ac+3ac+3bc+bc-2bc+2b²-b²=
=a²+2bc+b²=(a+b)²
№3
{3x-2y=14
{2x+y=7
{3x-2(7-2x)=14
{y=7-2x
{3x-14+4x=14
{y=7-2x
{7x=28
{y=7-2x
{x=28/7=4
{y=7-2×4=7-8=-1
{x=4
{y=-1