1) (2х – 1)(2х + 1) – (х – 3)(х + 1) = 18;

ploxomne: 4x^2 - 1 - (x^2 + x - 3x - 3) - 18 = 0
4x^2 - 1 - (x^2 - 2x - 3) - 18 = 0
4x^2 - 1 - x^2 + 2x + 3 - 18 = 0
3x^2 + 2x - 16 = 0
D = 4 + 4*16*3 = 196 = 14^2
x1 = ( - 2 + 14)/6 = 12/6 = 2;
x2 = ( - 2 - 14)/6 = - 16/6 = - 8/3 = - 2 целых 2/3

dmelnik302: 1) (2х – 1)(2х + 1) – (х – 3)(х + 1) = 18;